Terminology
Chemical rockets are rockets powered by exothermic chemical reactions of the propellant.
Rocket motor (or solid-propellant rocket motor) is a synonymous term with rocket engine that usually refers to solid rocket engines.
Liquid rockets (or liquid-propellant rocket engine) use one or more liquid propellants that are held in tanks prior to burning.
Hybrid rockets have a solid propellant in the combustion chamber and a second liquid or gas propellant is added to permit it to burn.
Thermal rockets are rockets where the propellant is inert, but is heated by a power source such as solar or nuclear power or beamed energy.
Monopropellant rockets are rockets that use only one propellant, decomposed by a catalyst. The most common monopropellants are hydrazine and hydrogen peroxide.
Read more about this topic: Rocket Engine