Falling in love with photography is easy. Being scared away by the highbrow photo terms is even easier. Crop-factor, aperture, depth of field... What the heck?!
Come on, it is not that complicated, you just need a minute to settle it all down, step by step.
Here's a rundown in plain English of the most common terms you'll hear or read about. Don't see a term defined? Just ask.
Aperture: Light passing through a camera lens must pass through a hole called an aperture. The aperture's size can be changed manually or automatically by the camera. The size of the aperture affects how much light gets through the lens and onto the film or sensor. Very small apertures increase the depth of field and require longer exposure times because very little light reaches the sensor. And very large apertures decrease the depth of field and allow for shorter exposure times. Aperture is measured by a number call the f-stop.
Back light: Typically, lighting comes from behind or to the side of the camera. Back lighting is light that comes from behind the subject towards the camera and is associated with increased lens flare.
Bracket (bracketing): To "bracket" means to take multiple photos of the same scene with different exposure settings. For example, you might bracket by taking three shots: one under-exposed, one correctly exposed, and one over-exposed. The common reason for doing this is safety in tricky lighting conditions -- to make sure that at least one of the photos will have the correct exposure. But there are other reasons: see HDR and Dynamic Range.
Camera: A lightproof box with a lens on one end that focuses light onto a film or digital sensor at the back.
Close-up: This is very similar to macro photography but with lower reproduction ratios. Magnification lower than 1:1 (for example, 1:4) are considered "close-up" rather than macro. See macro for more information about magnification
Crop-factor: Crop-factor describes the effect of using a lens on a camera with a smaller sensor than the lens was designed for. Because the smaller sensor can't take advantage of the larger image the lens creates, the effect is that the sensor records only the center portion of the image (effectively cropping the edges). Many DSLRs have around a 1.5x crop factor. Many people describe crop factor as a focal length multiplier because cropping decreases the field of view just like a longer focal length does.
Depth of field: This is the portion of a scene from front to back that is in acceptably sharp focus. Lenses can expand or contract the depth of field depending on the focal length of the lens and the aperture. If you've ever seen a portrait with a blurry background, you've seen a photograph with a narrow depth of field. And if you've looked at a landscape where everything was in focus from the closest flower to the farthest mountain, you've seen a photography with a very wide depth of field.
DSLR: A digital SLR. Exactly the same as an SLR except that a digital sensor is used to capture the image instead of film. See SLR.
Dynamic Range: Dynamic range refers to the range of brightness than can be recorded in a single image. The human eye has a tremendous dynamic range that allows you to see detail in dark areas and bright areas of a scene simultaneously. But cameras can't do this. Exposing to show detail in the dark areas may render the bright areas completely featureless (these all-white areas with no detail are called "blown" or "blown out" or sometimes "blown highlights"). And exposing to show detail in bright areas can render dark areas completely black. See HDR for one solution.
Exposure: The combination of shutter-speed and aperture that were used to capture an image.
Exposure compensation: Many cameras allow you to "dial-in" a certain amount of exposure compensation to either over- or under-expose a photograph. Over-exposed photographs are brighter and under-exposed photographs are darker. The typical reason people add exposure compensation is when the camera's light meter is not exposing the scene properly. For example, when shooting into a bright back light, most cameras will expose the scene so that the foreground subjects are dark. To brighten them up you need to add some positive exposure compensation to "over-expose" the photo.
Flare: Lens flare is characterized by hazy images, decreased contrast, and possibly even colored spots or lines in the frame. It is caused by intense light shining directly onto the lens.
Flash: The bright flashy thing that makes people blink when you take their photo.
Focal length: The length of a lens, usually expressed in millimeters. For example, a 50mm lens has a focal length of 50mm. Zoom lenses have variable focal lengths. The longer the focal length, the narrower the field of view becomes. The shorter the focal length, the wider the field of view. This is why lenses with very short focal lengths are called "wide-angle."
F-stop: This number is used to measure the aperture. The smaller the number, the bigger the aperture is. F-stop numbers are written like this: f/1.4.
HDR (HDRI): HDR is an acronym for High Dynamic Range (sometimes HDRI for HDR Image). HDR images are created by blending multiple, bracketed exposures of the same scene to create a new image with a wider dynamic range than could normally be captured in a single image. This allows scenes with very bright and very dark areas to be rendered in a way that looks more like what the human eye would see.
ISO: ISO refers to the sensitivity of the film or digital sensor. ISO typically ranges from 50 to 3200 with 50 being the least sensitive and 3200 being the most sensitive. Higher ISO allows you to use a faster shutter speed, all other factors being equal. Photographers will often increase the ISO when it starts getting darker rather than use a flash. Being able to change the ISO setting from shot to shot is great but remember that the higher the ISO setting, the more noise you'll see in your photos.
JPG: The standard image format of most digital cameras. JPG files have become a standard in digital imaging because the format is able to record a very high quality image while still having a very compact file size. One potential problem with JPG files is that each time you make a change to a JPG and save the file, it loses a little bit of quality. For this reason, always keep your original JPG in a safe location and if you decide to make changes to it save the changes in a separate file.
Lens: Lenses capture light and focus it onto the film or sensor at the back of the camera. Lenses are obviously a very important part of a camera. When a photographer refers to "glass" he is talking about lenses.
Macro: Macro photography generally describes photographing the very small. When people talk about macro photography, you'll often hear them talk about "reproduction ratios" or "magnification" and you'll see numbers like 1:2 or 1:1 or even odd ones like 1:7.1. What they are referring to is the scale of the object on film. A 1:1 magnification means that lens is focusing a life-size image of the object onto the film or sensor. A 1:2 ratio means that the lens is focusing an image of the object that is half life-size. And so on. True macro lenses are capable of 1:1 or higher magnifications.
Meter (metering): Most cameras have a built-in light meter that measures the amount of light in a scene and allows the camera to adjust the shutter speed and aperture for a proper exposure. To meter is to take a light reading.
Noise: Noise refers to the graininess of an image. Noise appears as random, grainy speckles throughout an image. Higher ISO settings typically create more noise.
Prime: A non-zoom lens.
RAW: RAW is a proprietary image format that some (typically high-end) cameras support. Every camera's RAW files are unique and require a special viewer for viewing and editing them. RAW files are also much larger than JPG files. As the name implies, RAW files contain the unprocessed (raw) data from the digital sensor at the time the image was made. RAW files contain much more information than JPG files which can give increased detail and more latitude during processing for exposure adjustments. You might think of a RAW file as the digital equivalent of a film negative.
Shutter: The shutter is a screen that covers the film or sensor inside your camera. When you press the shutter release button, the camera quickly opens and then closes the shutter to let just the right amount of light fall onto the sensor.
Shutter speed: The shutter speed is how long the shutter will remain open during an exposure. It is expressed in fractions of a second. Typical ranges for shutter speed are from 30 seconds to 1/8000 of a second. Fast shutter speeds can freeze action. Long shutter speeds may be required to capture very dark scenes.
SLR: Single Lens Reflex. It's a fancy name that means when you look through the viewfinder of your camera, you are actually looking right through the lens. What you see is what you get. This is different than most compact cameras which show you a view through a plastic window that is offset from the actual lens.
Telephoto: Telephoto refers to the long end of the focal length range. Anything longer than about 85mm is considered telephoto.
White balance: A digital camera tries to adjust the color of an image so that white objects appear white under the current lighting conditions. This is called white balance. Some cameras allow you to manually adjust white balance and many do it automatically.
Wide-angle: Wide-angle refers to the shortest end of the focal length range. Anything below around 24mm is considered wide-angle.
Zoom: A lens with a variable focal length.
These were the most common terms, though, as I wrote above - feel free to ask anything that is not 100% clear for you in the comments!