Software can include shareware, freeware, demos, multimedia files, program patches and upgrades. Some of these sites are basically online software stores, where you can search for, find out about, and download software to try or buy. These may include a rating system, descriptions of the software, how popular they are, compressed file size and other information.
Some sites guarantee software from their site to be virus-free.
Others sites for finding software are archie servers. The archie system is a collection of servers that allow the user to search a database containing lists of files available on hosts connected to the Internet. Archie is a search system that is useful when you know what you want to find on the Internet, but you don't know where to find it. Archie is a good place to search for public domain software. An archie server searches FTP sites for files, programs, directories, etc on a regular basis and stores the information that it finds in it's database.