These cumulative updates to Visual Studio 2013 include a variety of bug fixes and capability improvements.

Visual Studio Team Foundation Server Express 2013 provides the collaboration hub at the center of the Application Lifecycle Management (ALM) solution. By automating the software delivery process, entire teams can track team actions, transactions, and project artifacts such as requirements, tasks, bugs, source code, build results, and test results. Team Foundation Server Express 2013 enables comprehensive reporting and dashboards that provide historical trending, full traceability, and real-time visibility into software quality.
Note: TFS Express is limited to five (5) users. Larger teams can use Visual Studio Team Foundation Server 2013.

Support for Visual Studio 2013 is only provided on this current update, which is considered the Visual Studio 2013 Service Pack. The Visual Studio 2013 RTM version, released in November of 2013, will only be supported for one year after the release of this current update. For more information see the Microsoft Support Lifecycle Policy.

VS Release Notes
VS Known Issues
System Requirements
Compatibility