Check Out is the term used to describe the process of making a copy of a project from a repository into your local file system. This checked-out copy is called a working copy. A Subversion working copy is a specially formatted folder structure which contains additional .svn folders that store Subversion information, as well as a pristine copy of each item that is checked out.
You check out a working copy from the Repositories view. If you have not yet defined a connection to your repository, you need to add a new repository location.