The easy answer is to get the brand of camera that you want to get. There are some things that you should keep in mind when you're making your choice, though. If your camera can only hold 16 pictures then it's going to be inconvenient if you need to take pictures of 24 student projects. A camera that can hold 96 shots is a good start. Some cameras come with the cables and software for both the PC and the Mac.
Some cameras are larger than others.
A camera that fits in your purse or shirt pocket is much easier to keep with you on field trips, school functions, science fairs, etc. The answer is simple - digital cameras don't use film. By the way, this is the most common question that people ask me. Don't feel silly if you asked the question, though, many people are so conditioned to putting film in cameras that the question is just an automatic one that pops out before most people can stop it. Simply stated, the more pixels a camera divides a scene into then the higher the camera's resolution.