The more time you spend developing applications the more you come to appreciate software that tracks your revision history. A revision control system lets you create a sandbox for new approaches to problems, maintain multiple branches of released code, and provide a development history in the event of intellectual property disputes. Linux and Unix support many source code control systems ranging from the early and primitive SCCS and RCS to concurrent systems such as CVS and SVN and the modern distributed development systems such as GIT and FOSSIL.
The big advantage of Git and Fossil over older systems such as CVS and SVN is that a developer can use them without being connected to a network. Older systems such as CVS and RCS worked fine when you were at the office, but you could not check the new code or examine the old code while working remotely.
Git and Fossil are two different revision control systems...