Basically there are:
Static Body - it don't move, where you put it in the game it will stand, can collide with RigidBody and KineticBody. And it can function as a escalator or conveyor belt;
Kinetic Body - you need coding to control or move it. It is used to player characters;
Rigid Body - it is the one which has Physics simulation and can be one of four Modes, Rigid (full Physics simulation) or Character ( has Physics simulation but doesn't rotate) or Static or Kinetic. To code you need to use Godot's Physics system, you can't simples code any of the RigidBody to one side or another, Physics forces need to be applied to them so they can move.