You can also view previously answered questions in the HSW Question Archive . In general, if you are e-mailing the pictures to friends who will view them on a computer screen, you will want to send them pictures in the jpeg format at 640 x 480 pixels. If you are printing the pictures, you need about 150 pixels per inch of print size. So you would not want to print your 640 x 480 images at a size bigger than 4 x 3 inches.
Cameras can be quite complicated and use unintuitive jargon.
Your camera probably has several different picture quality and picture size settings. For example, we'll go through all of the quality settings of one of the cameras we use at How Stuff Works . We took the same picture in all of the different modes and here are the results. This is a compressed format that reduces the file size of the images. Generally you will want to use the jpeg format because the uncompressed pictures will quickly eat up the storage space on your camera.