Directly access the Source Repository to copy the source code as it currently is with a full history of all changes. In Git this is know as Cloning the repository, in Subversion it is Checking-Out the code. This is most commonly done if you want to actively develop the code.
Download a tarball snapshot of the Source Repository to bootstrap a Git clone or Subversion checkout. This is a good option if you have a slow or unreliable internet connection. See the Source Snapshots page for more details.
Download a tarball snapshot of just the code as at a given time or release. This is most commonly done if you do not want to develop the code itself but just want to use it for a stable system installation, testing a release, or developing applications outside of the KDE Community.