Visual Studio solutions can be very large, containing tens to hundreds of source files. The programmer can get lost when navigating the code of such large solutions. One feature that helps is to know where the currently active (or open) source file is in the Solution Explorer pane. If the source files are hierarchically organized in the Solution Explorer, this can be a big help.
This feature is not turned on by default in Visual Studio. To turn it on, click Tools → Options. Go to Projects and Solutions → General and check Track Active Item in Solution Explorer.
Tried with: Visual Studio 2008 and Visual C++ 2010 Express