Software used to manage changes to documents, computer programs, large web sites, and other collections of information.
Version control systems (VCS) most commonly run as stand-alone applications, but revision control is also embedded in various types of software such as word processors and spreadsheets, e.g., Google Docs and Sheets and in various content management systems, e.g., Wikipedia's Page history. Revision control allows for the ability to revert a document to a previous revision, which is critical for allowing editors to track each other's edits, correct mistakes, and defend against vandalism and spam.
If your request is rather targeted at a specific VCS, please first ensure there's not a more specific tag available. For your convenience, some of those are listed below.