Final answer:
The Aztecs and Mayans were ancient American civilizations. The Aztecs had a supreme ruler and practiced human sacrifices, while the Mayans were organized as city-states and had a complex writing system.
Step-by-step explanation:
The Aztecs and Mayans were both ancient American civilizations encountered by the conquering Spaniards.
Some of the important differences between the two include the fact that the Aztecs were ruled by one supreme ruler, while the Mayans were structured as a network of city-states with their own rulers.
Additionally, the Aztecs were known for their practice of human sacrifices, while the Mayans had a more complex writing system and possessed a written language.