This tutorial is generic and applies to electronic photo editing and creation.  There are many more extensive tutorials on the internet.

There are several File Formats:

• JPG:  Good for publishing on the Internet, Most portable of all the file types.  Can be "compressed" to reduce file size and image quality.  Editing reduces photo quality kind of like making a copy of a copy.   Don't use compressed files for permanent photos.
• GIF:  Limited color palette.  Good for clipart, or black and white line drawings. Can be animated.
• PNG: (Portable Network Graphic)  Improvement over both JPG and GIF.  Not fully supported by browsers.  Very Large file size
• TIFF: (or TIF; Tagged Image Format)  Large file size but good support by most image editting programs.  Very Large file size.
• SVG: (Scaleable Vector Graphics) Large file size; partly supported by recent brpwsers.  Images can be scaled with no lose of clairity.

Usage:

• TIF: Use for the best picture clairity and permanent photos.
• JPG: Use for posting photos to the internet and web pages.  Do not use for permanent photos or if you are editing a phtot.

Most image editing software uses it's own proprietary format.  They do this so you can't switch to some-one elses software.  AND they can (over)charge more for their software.

Use either TIF, PNG (preferred), or your image editting software's proprietary format for photos you want to save permanently.

Send photos to other people as TIF, PNG, or JPG files.  Don't compress the JPG files before sending.