TFS allows to access pre-build reports which are part of Microsoft SQL Server Reporting Services. These are several reports that come with the TFS and creation of each project replicates those reports into SQL Server Reporting Services.

TFS Reports can be located in the Team Explorer under reports folders. Each report can be updated, removed or deleted from TFS Project via Team Explorer. Once report is deleted from the TFS Team Explorer you will no be able to recover this report and you need to ensure that copy of the report is store in SourceSafe repository on the server.

 
TFS Reports

TFS uses SQL Server reports that are nothing more then just an XML file store on the SQL Server reporting engine and can also be access and view via web browser.

Here is an example of the report rendered within Team Explorer.

 
TFS Report Sample

TFS reports is just SQL Reports and can be accessed and worked on from within SQL Server Reporting Services.

 
TFS Reports List