Subversion (SVN) is centralized revision control version. That means you have one central server and many SVN clients installed on developer’s workstations. When a developer commits, code updates are sent to the server immediately (in contrast to Git, where commits stored in local repositories and pushed to the central repository manually).
Anyway SVN is very old and inflexible revision control system – it has many disadvantages comparing with Git. But it is used for some old projects and it can be useful to know some basic SVN commands.