system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: The basic differences between the Incas, Mayas, and Aztecs.

If you wouldn't mind sacrificing some of your time, I'd appreciate it.
gpt
The Maya is a Mesoamerican civilization, noted for the only known fully developed written language of the pre-Columbian Americas, as well as for its art, architecture, and mathematical and astronomical systems. Initially established during the Pre-Classic period (c. 2000 BC to AD 250), according to the Mesoamerican chronology, many Maya cities reached their highest state of development during the Classic period (c. AD 250 to 900), and continued throughout the Post-Classic period until the arrival of the Spanish.

The Inca Empire or Inka Empire was the largest empire in pre-Columbian America. The administrative, political and military center of the empire was located in Cusco in modern-day Peru. The Inca civilization arose from the highlands of Peru sometime in the early 13th century.

From the 13th century, the Valley of Mexico was the heart of Aztec civilization: here the capital of the Aztec Triple Alliance, the city of Tenochtitlan, was built upon raised islets in Lake Texcoco. The Triple Alliance formed a tributary empire expanding its political hegemony far beyond the Valley of Mexico, conquering other city states throughout Mesoamerica. 

TL;DR Differences: Different people, different places. Mayans came before the others.