- Ultra compacts typically lack manual controls but are the smallest and most convenient.
- Compacts are a little wider and thicker, often have manual controls, and are still small enough to carry with you.
- Faux DSLRs go by a few names, they're cameras that look like DSLRs but only have one lens and they're usually portable enough to fit in large pockets.
- DSLRs are the big boys of the consumer camera world. They usually feature extensive manual controls, they're fairly large and can be difficult to carry around, and they allow you to switch out lenses. They also feature the best low-light and image quality. Unfortunately, this comes with a huge price increase.
- Megapixels - Any modern camera has more than enough megapixels to take care of most printing needs. If you need something the size of a poster, you'll want to look into higher-end SLRs. If all you want is 4x6s or 8x10s, you're fine with anything released in the last 2 years.
- Optical Zoom - Most cameras only report their optical zoom but some still list their digital zoom as well. Always ignore digital zoom. It's digitally zooming in on your image the same way you would in any program, it degrades image quality. Optical zoom is the only important measurement. It means how many times the physical glass in your camera can magnify the image. Most compacts are around 3-4x, some of them can get up to 12x. DSLR's vary depending on the lenses you purchase.
- ISO - The easiest way to put this is ISO will enhance your camera's performance in low-light but it raises the digital noise in an image. That results in color distortions and degrades the look. In most situations, you'll want to shoot at the lowest ISO possible, usually 100. During low-light conditions, it may be required for you to raise your ISO to 400, 800, or even 1600. Just keep in mind on most compact cameras, ISO 1600 may make your image unusable. With a DSLR, it can still come out great.
- Macro - This is a special focusing mode for close up photography. If you want to take pictures of smaller things such as bugs, coins, miniature items in general, this is a mode you'll want to have. Most compacts have this mode and certain DSLR lenses have this as well.
- Compact Flash / SD / SDHC / etc. - These are all examples of memory types used in cameras. There are a few more such as the Sony Memory Sticks or Olympus xD. The primary thing you need to worry about is buying the proper memory card for your type of camera, which is always mentioned on the box and product descriptions of the camera.
- Batteries - Most first party batteries are a huge source of profit for the camera manufacturers. They're expensive and little better than the third party batteries you can purchase from Ebay. A few cameras have firmware that require you to use official batteries, this is often mentioned in reviews. Keep an eye out, it'll cost you money down the line.
- Image Stabilization - This is a mode offered on recent cameras that digitally reduces the shake of holding a camera, it helps reduce blur and makes it easier to shoot in darker situations.
One thing you're likely to notice while looking over a variety of cameras is most of them mention specific modes, facial recognition, D-Lighting, all sorts of features that may help you out a little bit but aren't a big deal. Certainly not worth basing any of your purchasing decisions on. With the above terms in mind, you should be a far more informed camera shopper.