Where did Aztecs come from?

I was just wondering,are Aztecs and Native Americans the same thing?Did Aztecs migrate from North America to Central America and form their own culture?The reason I ask is because I live in Memphis TN,and we have an Indian Village here(Chucalisa)and there is this thing made of mud that resembles the Mayan and Aztec Tikals?If Aztecs didn't come from North America,then where did they come from?Thnks