TortoiseSVN is a Windows shell extension which adds Subversion information and commands to Windows Explorer.
TortoiseSVN is Subversion for most Windows users. TortoiseSVN brings the full functionality of Subversion into the Windows shell.
There are also some very useful extras. Most notable is the "Repo-Browser" which enables queries and changes to be made directly on the repository.
TortoiseSVN Context Menu
As you can see from the screen dump of the context menu, TortoiseSVN offers plenty of functionality. Most of the menu entries use the same terminology as the Subversion command line client. Some operations use different names. The Subversion copy command is under Branch/Tag which is what most people use copy for. The relocate entry is equivalent to the svn switch --relocate command.
TortoiseSVN includes TortoiseMerge which can be used to view diffs prior to a commit or to resolve conflicts after an update.