Question

In the context of studying major bodies of our solar system, what category of object does our moon best fit?.

Answer 1

The simplest, obvious category is " Satellites " .

But there's a lot of good reason to call it "Component of Binary Planet" .

As a fraction of the size and mass of its planet, our moon is the largest in the solar system.  

Several writers have pointed out that an alien astronomer studying our solar system might describe the 3rd body from the Sun as a "Binary planet".