Digital images are generally saved in one of a handful of common formats. Let's go through the most common types of files and what each is best for.
RAW is a lossless, uncompressed file format that contains the raw data from a camera's imaging sensor. Because it contains all the original image data, users can sharpen, resize, or crop the picture without losing any quality. However, RAW files are large - they can run more than 50 megabits - too large for sharing. RAW is best for storing images in their original quality. RAW formatted photos are also incompatible with many photo programs because each camera maker has its own RAW format.
TIFF is a lossless, uncompressed file format like RAW. Because it's not compressed, TIFF files retain a photo's color information. TIFF files can be edited and copied again and again without losing picture quality. This makes them an ideal format for editing photos and making prints, and for this reason it is a common format used by photo editing software programs. TIFF files tend to be between 5MB and 15MB, too large to easily share.
JPEG is a high-resolution compressed file format. Compressing files makes them smaller and easier to share. However, photo details are left out, affecting the quality. The more a JPEG file is compressed, the lower the quality of the photo. JPEG is best for sharing photos through email and on the Internet. However, it also is a lossy format and its quality deteriorates each time it is edited or copied.
PNG is a lossless compression format commonly used for images posted on websites and in graphic design. PNG offers more color depth and transparency than JPEG files, making it easy to mix images and text.
GIF is an older uncompressed file format that supports a limited color palette. It's best used for clip art and icons, not photographs.