What happens when you click "Build Solution" in Visual Studio?

You probably know that msbuild.exe is somehow involved when you click "Build Solution" from the "Build" menu within Visual Studio.
But msbuild.exe is not called directly, instead Visual Studio does the same as you would call "devenv.exe /build" from the command prompt. The executable has to be passed the name of the solution together with the desired solution configuration.
devenv.exe is more or less a wrapper that calls msbuild.exe with a set of properties that are visual studio specific.
Note that devenv.exe only comes with an installed Visual Studio, msbuild.exe is (easier) available with the .NET Framework installation.