Nahuatl is a language that was spoken by the Aztecs in ancient Mexico a long time ago. It is still spoken today by some Mexican people. The language has a lot of different words to describe things and ideas, like colors and emotions. It also has different ways of saying things depending on who you are talking to, like if you are talking to a boy or a girl, or if you are talking to someone older or younger than you. Nahuatl is a very important part of Mexico's history and culture.