VS History Files for Visual Studio saves a copy of your files every time you save them. They are stored in a compressed .vshistory directory in each project and can be opened or differences with the current file can be viewed by right clicking the file in the Solution Explorer.

A custom VS History tool window displays each version of project files as they're saved. Each version can either be viewed in a VS window or a difference between that version and the current file.

VS History settings allow the user to select how many versions should be maintained:

Keep all versions
Keep "n" versions
Keep versions for "n" days
Keep versions for "n" months

A display of *all* VS History files is available in settings: