A small application designed to reside on a PC desktop (Mac OSOS (Operating system)An operating system (OS) is a set of programs that manage computer hardware…//read more  X or Windows Vista) or within a Web-based portalPortalA Web site that often serves as a starting point for a Web user’s session. It…//read more  or social networkSocial networkAn online destination that gives users a chance to connect with one or more…//read more  site (e.g., MySpace or Facebook) offering useful or entertaining functionality to the end user.