Camera For Dummies: Other jargon

Hope you already had a look at the previous 3 posts:
Camera For Dummies: Basics
Camera For Dummies Basics: Aperture
Camera For Dummies Basics: Shutter Speed

This post is all about the other common jargon used in photography.

Exposure/Exposure-level:

Exposure, at it's most basic, is a combination of the current values of Aperture and Shutter Speed settings. As we discussed in related posts on each of these, the aperture is the size of hole in lens through which light passes to expose the film and shutter speed is the length of period for which this light is allowed (by shutter) to pass. Overall amount of light required to get a properly exposed photograph is obviously affected by both these settings.
See also exposure compensation.
Note: If your photo is underexposed (dark) then you can always use some basic photo editor (e.g. Picasa) to "Fill light" manually, which gives you the same effect. Opposite is also true, overexposed => add "shadows".

ISO setting:

Back in old days before Fuji and Kodak stopped making films for film (AKA analog) cameras, films were categorized by their sensitivity to light. ISO provided a scale for sensitivity and it became the standard. The digital cameras carry over this legacy, by providing a setting called ISO setting, which has the same effect, except that it's for the sensor instead of film.
Most normal films are/were ISO 100, with 200 or 400 being the most commonly used by amatur photographers. Higher the number the more sensitive the film to light, thus helping achieve exposure required for a decent photo in shorter time and/or with smaller aperture.

Metering Mode:

On a digital SLR, when you set the mode to A (automatic) or P (Program), the camera decides the exposure-level when you click. It does so by analyzing available light in the framed view. Analysis here is what metering is. You have the option of selecting from a few basic modes available on most DSLRs.

Most versatile mode is the "Evaluative Metering" (AKA matrix, evaluative, honeycomb, segment metering, or ESP (electro selective pattern)), which basically considers the light available in whole frame to decide exposure.
Center Weighted Metering: In this case, the camera evaluates the light available in some specific area (usually 60-70% of center of the frame) and decides on the exposure. This is useful when taking pics in high contrast situations, e.g. a group of friends standing in front of a well lit building, with Evaluative Metering you'll end up with a photo where everyone's face is black and building is beautifully exposed (clearly visible details).
More expensive cameras allow user to select the weight and a off-center area.
Spot Metering: This is an extreme version of Center Weighted Metering, where the camera considers only 1-5% of area around selected spot in the photo. Some cameras allow you to select the "spot" some consider only center.
Multi Spot Metering: Same as Spot metering except you can select multiple "spots". Most cameras that provide this feature also allow you to select the spots.

Here is an excerpt from the Canon EOS 1d manual on supported metering modes:

Notes:
1. When dealing with bright backgrounds (e.g. subject standing in front of bright light/sun) or contrasting amount of light (bright moon in a black night sky), evaluative metering would under or over expose the subject respectively. Use center weighted or spot metering in such a case.
2. A nice trick that most DSLRs support is Exposure Locking (on Canon EOS series it's called AE lock). E.g. when taking a pic of a beautiful skyline with clouds, you would have top half (sky) of frame very bright and bottom (land) very dark, evaluative metering would always over-expose the sky, you'll see the details on ground would be nice but sky would be just white blank. In such a case, point your camera to the sky such that only sky is in frame, press the shutter button halfway until camera decides and locks the exposure levels, now reframe (point) the camera to include the ground too (holding the shutter button pressed half way), click! This way camera would ensure the details in sky are visible as exposure setting are based on light in the sky.

Lens types:

Prime & Zoom: Prime lenses have fixed focal length, e.g. Canon EF 50mm f/1.4, whereas zoom lenses can zoom in or out over a focal length, e.g. Canon EF 28-105mm f/3.5-4.5
Fish-eye, Wide, Normal/Standard, Telephoto: These are lens categories based on their focal length from smallest focal length (fish-eye - less than 16-18mm) to biggest (telephoto - more than 120-150mm). Words like ultra, super, medium are thrown in to differentiate within each category, e.g. a Medium Telephoto has smaller focal length than a Super Telephoto.
Human eye's focal length is close to 50mm (on 35mm or full frame scale), so 50mm lens is often known as the "normal lens", wikipedia defines it as: "In photography and cinematography a normal lens is a lens that reproduces a field of view that generally looks "natural" to a human observer under normal viewing conditions". On an APS-C camera equivalent would be 50/1.6 ~ 30mm. See "Full frame and APS-C below".
As a rule of thumb, lenses wider (smaller in focal length, wider in angle of view) than 50mm are called "wide angle", lenses narrower (bigger in focal length,  narrower in angle of view) are called telephoto lenses.

Full frame and APS-C:

Back in old days of film cameras, the usual size of each negative (film) was 35x24mm in size. This was known as 35mm film. In the world of digital cameras, sensors replace film, so equivalent sensor of 35mm film is called "full frame" sensor. Similarly APS-C in digital is equivalent of APS (~22x15mm) in analog/film world. APS-C sensors are about 40% smaller than full frame in general. What's the point? Well, given the size if APS-C is 40% smaller than full frame or the 35mm frame, a photo taken on APS-C (compared to photo taken with same lens on same focal length/settings on a full frame) is cropped by 40%, or in other words it looks like it's taken at 1.6 times the focal length. See this for detailed explanation.
One big problem this causes is that all lenses' (SLR/DSLR lenses) focal length specs are given in their 35mm equivalent. So when you buy a Canon EF 50mm lens and put it on a Canon EOS Rebel Ti (an APS-C camera) you effectively get 50x1.6=80mm lens. So when you buy an expensive 7-14mm fish eye lens it becomes 11.2-19.6mm on an APS-C camera. :-((
Most amateur DSLRs are APS-C. A full frame DSLR usually costs much higher ($3000+ from Nikon and Canon).
For any amateur photographer I recommend to have at least one wide-angle (less then or equal to 28mm), one normal and one telephoto (80-120mm) lens. You can also have a single zoom lens that covers the required range e.g. "Canon EF 28-135mm f/3.5-5.6 with IS". But on an APS-C DSLR it would become 1.6 times viz 45-216mm. But usually Canon/Nikon ship their APS-C camera bodies in a kit with an 18-35mm lens (18x1.6=28.8mm).
One of the best lenses to start learning photography with a normal prime lens!
PS: These are just the 2 most common formats, there are other as well.