Jenkins is a continuous integration instrument utilized during application development processes.
It is a server-based program that supports such version control instruments as AccuRev, Git, Mercurial, Perforce, Clearcase, etc. and operates in a servlet container.
Jenkins is written in Java, but there are a lot of plugins for it making it suitable for projects in various programming languages besides Java.
The tool is free, it is applicable for various platforms. It was released for the first time in 2011.