Source Control Management (SCM) is the name given to the method of working with sub-versions or backups of your projects through a repository and local source. Basically, an SCM solution is an independent software package which controls all the aspects of maintaining, changing and comparing versions of your projects as you work on them. This is especially useful to those that work in a team and need to be able to control who does what and not worry about losing data or making changes that may need to be undone at a later date, but individuals can benefit from this powerful yet flexible system too.
We recommend that you have some working knowledge of how source control works before attempting to use it in GameMaker: Studio.
There are various SCM tools available to you, and GameMaker: Studio permits you to use the three most popular:
NOTE: You can use other SCM solutions, but these are the ones that GameMaker has tutorials and default configurations for. Other tools will require you to set up custom profiles, which are explained briefly on the page Source Control Preferences.
If you are not too familiar with SCM solutions then we recommend you use SVN and install a user-interface like TortoiseSVN. GameMaker: Studio comes bundled with the 1.7 and 1.8 versions of SVN by default, so if you use this option make sure that the user-interface you use is for the either of the those versions (preferably the 1.8 version). Both GIT and Mercurial are advanced SCM solutions and require that you have a good working knowledge of how SCM works, and prior experience with both is a benefit if possible.
To help you get the most from SCM with GameMaker: Studio we have compiled a series of articles which cover the very basics right up to creating your own configuration file for GIT or Mercurial.