VCS Root
VCS roots are a collection of VSC settings (paths to sources, login, password, and other settings) used by TeamCity to obtain the source files for your builds. The VCS roots are monitored by TeamCity, so that any changes uploaded to the version control system are shown in TeamCity's user interface. In many cases, you'll want to set up your build configuration to trigger a new build when TeamCity detects a user has made a change to any of the build configuration's VCS roots.
By default, VCS roots can be used by all of the project's build configurations. VCS roots can also be "shared", which means they also can be used by different projects in TeamCity.
For the VCS roots under ClearCase, CVS, Perforce, StarTeam and Subversion, TeamCity can label the source files of the builds. If Configuring VCS Settings is enabled, and the labeling format is defined on the 2.Version Control Settings page, the labels appear in the build results page.