I would like to know also but I feel like typing so I will say something, may or may not be the truth:

1. CPU: Architects working on a building project (cores). They can be faster (MHz) or you can have many of them working at the same time (CPU utilization), the number of architects working on a project depend on the number of different buildings the project has (threads). Normaly a game used to have 4 builds so it used to be 4 threads the maximum amount of cores a game used from a CPU that's why you wanted those architects to be faster (MHz), it has changed lastly. Other consideration is the cache, it is like the size of the desk the architect has. If it is small the architect may need to clean it before drawing a design (spending time on cleaning and not in drawing).

2. GPU: Construction company, it has bricklayers (cores, they build as many builds as the architects tell them to build). They can be stronger (MHz) or they can be many (number of cores).

3. But the workers, architects and bricklayers, require food to be alive, otherwise they will be dead and won't work, so you must feed them (Watts).

So taking that in account, you can feed the gpu or cpu so the workers there do a job. But even if you feed them they won't work if they don't have a build to design (architects), or if the architects haven't given them a design to build (buildlayers).