As the name suggests, multi-agent systems are a kind of simulation model that uses multiple interacting agents for understanding the process.
In am multi agent system, multiple autonomous agents are modelled based on how they interact, and perform actions based on the goals and preferences of the (real-world) entities they represent. These are often inteconnected through a system, such as a heirarchical arcitectures which related their interdependencies.
Source: https://link.springer.com/chapter/10.1007/978-3-319-92447-2_27