MSBuild uses the vcxproj files as input to control the build process. These are XML files containing a series of build steps and commands. These invoke the compiler, linker, and various other tools required to build a project, much in the same way a Qt Creator kit does. You still need a compiler, linker, and all of the other tools installed - MSBuild does not include them. So a Qt Creator kit and MSBuild are two different ways of doing the same thing and are compatible only at the level of the tools each one uses to build a project.

You've probably found the MSBuild documentation from Microsoft. It has examples of how to build a vcxproj file by hand. Normally you would use Visual Studio for this, but if you have a project file, you can run MSBuild from the command line.

Is there a reason you must use MSBuild standalone and not with a Community Edition of Visual Studio?

You might also consider cmake. From what I understand, Qt6 will be using that for builds.