Returns a string containing details of how far the host sytem can use the directx 11 functionality

Valid returned values are

Directx 11 not installed -Indicates that the host system does not have directx 11 installed
Directx 11.0 features - Can fully use the directx 11 functionality
Directx 10.1 features - Can emulate the capabilities supported by directx 10.1.
Directx 10.0 features - Can emulate the capabilities supported by directx 10.0.
Directx 9.3 features - Can emulate the capabilities supported by directx 9.3.
Directx 9.2 features - Can emulate the capabilities supported by directx 9.2.
Directx 9.1 features - Can emulate the capabilities supported by directx 9.1.
Unknown feature level - Returned if an unexpected feature level was found

Please see http://msdn.microsoft.com/en-us/library/windows/desktop/ff476329(v=vs.85).aspx for more information on feature levels