SCM stands for Source Code Management. Pretty much the same thing can be called VCS, Version Control Software. Perhaps even more TLA’s are there out in the wild. It all boils down to a program which allows programmers to manage their source code.
Pretty much everybody who started using SCM, started with CVS and then moved to something else. Probably Subversion, which is meant to be a CVS replacement. For more adventurous or demanding developers, there are many other SCM’s: Git, Bazaar, Monotone, Mercurial, Darcs… and more.
Mark Shuttleworth has written an interesting thing: that file and directory renaming is one of the most important operations to be handled with an SCM. I got curious and wrote a test case for three SCM’s I know: Bazaar, Git and Subversion. The scenario is: