A parrot is a brightly colored tropical bird with a distinctly loud voice. If you see someone calling a colorful bird "Polly" and asking it if it wants a cracker, that's a parrot.
Parrots are popular pets because many of them have the ability to mimic sounds they hear, sometimes including human speech. In fact, this skill has led to a secondary meaning of the word parrot, "mimic mindlessly." You could say, for example, "I'm not going to just parrot everything the teacher says — I'm no parrot." The origin of the word is uncertain, although we know that before parrot, this bird was called a popinjay.