Single Agents:
1. When there is only one agent in a defined environment, it is named the Single-Agent System (SAS). This agent acts and interacts only with its environment.
2. Single-agent systems are centralized.
3. A "single-agent system'' should be thought of as a complex, centralized system in a domain that also allows for a multi-agent approach.
4. A single-agent system might still have multiple entities - several actuators, or even several robots. However, if each entity sends its perceptions to and receives its actions from a single central processor, then there is only a single agent: the central process.

Multiple agents:
1. If there is more than one agent and they interact with each other and their environment, the system is called the Multi-Agent System.
2. Multiagent systems can be viewed as having dynamic environments.
3. Multi-agent systems can manifest self-organization as well as self-direction and other control paradigms and related complex behaviors even when the individual strategies of all their agents are simple.