JPG vs GIF vs TIFF
So when you scan, you might see a few different image formats. You should be familiar with at least one of them - the JPG (or JPEG). You might also be familiar with the GIF. You may not, however, be familiar with TIFFs. Here's a brief explanation of each file-type.
JPG: This is an image format that you can set the quality of. It's the most widely used format of all images, and has distinct advantages and disadvantages when it comes to file size and clarity.
GIF: Limited to 256 colors, GIF images aren't the best choice for scanning photographs, but their small size does make for a passable black-and-white document format. However, not all scanners offer the ability to scan files as a GIF, and unless you are really worried about the size of the file, I would not use GIF.
TIFF: TIFF (or TIF) files are simply high quality bitmap files with minimal compression, making them fantastic for high resolution scans that are to be printed. They tend to be big images and the file-size is often quite large.
Looking to learn a little more about file formats? Check out Image Formats: What are the Advantages and Disadvantages of Image File Formats on the Web?