These are some simple rules for each of the known filetypes, so that the next time a friend or a family member wants to know what they should use you can impress them with your smarts. In order to remain a free and useful service, all photographs submitted will be JPGs. The following is for your personal benefit.
JPG - This is the format of choice for nearly all photographs on the web.
GIF - Do not, I repeat do not use GIF for photographic images. GIF works well with solid colors.
TIFF - This is usually the best quality output from a digital camera. The file size is huge compared to even the best JPG setting, and the advantages may not be noticeable. It is recommended that you stay away from this setting.
PNG - is similar to GIF, but it supports 16 million colors not just 256. If you want to display a photograph exactly without loss on the web, PNG is your choice. With respect to ease of use, it is recommended that you just use JPEG
BMP - is an uncompressed proprietary format invented by Microsoft. There is really no reason to ever use this format. Say it outloud with me now, "Microsoft sucks." Very good!