Cervisia is a user friendly version control system front-end. The aim is to support CVS and other version control system programs in a unified interface, featuring conflict resolution, difference and history viewers, status for the working copy files, and support for most version control functions. You can get Cervisia by building the kdesdk module or installing the kdesdk package provided by your distribution. Currently, only CVS is supported, but other version control systems may be integrated in the future.
A version control system is a tool to record, manage, and distribute different versions of files. CVS is a version control system. It allows you to share your modifications easily, as each of the contributors can work on their local copy at the same time, without fear of overwriting each others' modifications. It allows the recovery of past versions (useful for tracking bugs), the creation of branches (for experimental development or for releases of code) and more.
The main repository usually holds a collaborative project (commercial or not), but you can take advantage of the nice revision control features offered by CVS even for a project developed exclusively by you. It is easy to set up a local repository, and you will gain the ability to track changes that caused bugs, revert changes, avoid accidental loss of information, etc..
The repository holds the project files, and every contributor keeps their own local copy, named working copy or sandbox; one can then add their modifications to the main repository (a process called "committing") and/or update their own copy to reflect recent changes made by other contributors.