JPEG or .jpg
JPEG stands for the Joint Photographic Experts Group. This is a group of experts who defined a standard compression scheme for still images, commonly called JPEG Compression. Images compressed in this way are called JPEGs.

GIF or .gif
GIF (Graphics Interchange Format), a graphics format popularized by CompuServe in 1987, produces file sizes that are smaller than most other graphics types. GIF graphics can be viewed on virtually any platform.

.pdf
PDF stands for Portable Document Format. A .pdf file is specially formatted for easy downloading, viewing, and printing on a variety of computer and browser types. To view or print .pdf files, you must have the Adobe Acrobat Reader installed as a helper application.

.mov Quicktime VR
Please see How do I view QuickTime VR images? in the Video section.

.bmp
This is a Windows file format for bitmap images

.ico
This is a Windows file format for program icons.