The purpose of a debugger such as the gnu Make debugger is to allow you to see what is going on “inside” the gnu Make debugger when it processes a Makefile.
The gnu Remake debugger can do four main kinds of things (plus other things in support of these) to help you catch bugs in the act:
Although you can use the the gnu Make debugger to debug Makefiles, it can also be used just as a front-end for learning more about Makefiles and writing them with gnu Remake.
A degenerate and less-interactive form of debugging is tracing in which one passively watches some of the steps that go on in processing a Makefile.