A solar system consists of a star and all the objects orbiting it as well as all the material in that system.

Our Solar System includes the Sun together with the eight planets and their moons as well as all other celestial bodies that orbit the sun. 

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A dwarf planet is an object in orbit around the Sun that is large enough (massive enough) to have its own gravity pull itself into a round (or nearly round) shape. Generally, a dwarf planet is smaller than Mercury.  There are three known dwarf planets. Ceres, Pluto, and 2003 UB 313. There may be dozens or perhaps more than 100 waiting to be discovered.