diesel is a type of fuel. the kind used in mass transportation most often because it is very cheap and efficient. the rc plane version is diesel kerosene which is more flamable nad smells really wierd. Two strokes are a type of engine. two stroke means that there are two movements of the piston before the cycle is complete. this is not probably the most accurate explanation but i am going to sacrifice some accuracy to make it simple as it would take a page or more to be accurate. on the piston's upstroke a little rotating hole in the hollow crankshaft under the carburator opens up and the upward motion of the piston sucks in air. meanwhile, as the piston reaches tdc (top dead center) the crankshaft rotates and shuts off the opening so the fuel air mixture is trapped. you get combustion from the previous cycle and the downward motion of the piston compresses the trapped mixture in the crankcase. the piston hits the exhaust port and the hot gasses are released. jsut past the exhaust port is the intake port where the compressed mixture is forced into the chamber and the cycle goes on.