Kerbin

Kerbin is the home planet of the kerbals. It is quite obviously the ksp analog for earth. Kerbin is where the helm of the kerbal space program is operated, at least in the early stages of the game. For gameplay reasons, it is 1/10th of the size of earth, which is even smaller the real life moon. In the official dev videos, kerbin is shown to have clouds in it's atmosphere which is a step up from ksp 1, because there were no clouds at all on any atmospheric world except for jool, and you had to get mods if you wanted them.