The common themes of Mesoamerican mythology is duality, death and the underworld, a multitude of gods and goddesses with different functions and manefestations, sacrifice, cyclical time and the progression of creation episodes.
Mythology is a way to explain the beginning (creation), the place people occupy in the universe, what things are the most important, and why things are the way they are. It is the equivalent of the science and major religions of our day as they also speak to these exact same questions, though the method and answers are different.