FILES!

"There are reasons for each of these types of file to exist. If there were not, then there would be no arbitrary new file types propping up here and there."
-Perez

.TIFF: A file format that does not lose information when saved. Saves layers, paths, and all graphic data. This is usually a large file.
-If you use image compression on a TIFF, you are not going to lose any information. There is a difference in the "byte order" of an IBM PC and a Macintosh.

.JPEG: An image file which loses information by compressing graphic information. It's difference on the screen is not noticeable; when printed out though, there is a noticeable different. The difference between a file like a .TIFF and a .JPEG is similar to the difference
between a .WAV and a .MP3. There, to the less-trained eye or ear, is essentially no noticeable
difference.

.PNG: does not lose information. Does not save layers. Compresses to smaller file than TIFF.

.GIF: Like a jpeg. Loses information by compressing. Can't save layers. Saves as INDEXED COLOR file not RGB or CMYK. Browsers can see .GIFs.