Understanding how revision control systems function is important for today's software ecosystems -- Revision control systems not only help in building better scientific software, but also help in improving developer productivity for a project.
Revision control systems are essential for managing changes to files in a team-wide setting and thereby keeping track of changes to a software development project as a whole.
The short document What is Version Control provides a brief overview of revision control systems and how they are useful in many projects (not just managing software source code). This document reviews some important terminology and briefly outlines popular tools for revision control--Git, Mercurial (hg), Subversion (svn), and CVS---and how they relate to each other. The document also outlines common and helpful use cases for revision control tools.