Asteroids are basically small, lop-sided planets that move in elliptical orbits, generally between the orbits of Mars and Jupiter. The largest asteroids in our Solar System are 1 Ceres, 2 Pallas and 4 Vesta.

Asteroids are identified by both name and a number given in the order of discovery. When an astronomer notices a possible undiscovered asteroid, it is 

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reported and other astronomers observe it over a period of time to determine if it is new.  Once it is identified as new, the International Astronomical Association gives it a number and then the astronomer who discovered it gives it a name.