His style of music is called "hip-hop." He was born in Seattle, Washington. He is best known for his hit song "Baby Got Back". That song has catchy phrases and cheap humor, and it talks about liking women with big buttocks. This made it popular in the United States during the 1990s.
Sir Mix-a-Lot is not actually a peer of the realm but has assumed the title 'Sir' for humorous or ironic effect.