Actor

An actor is a participant in a system.

These systems can be anything:

• markets
• social networking platforms
• a football game
• operations in a corporation
• software

A system modeled using the concept of an "actor" is said to be using the "actor model".

In the actor model, an interaction from one actor to another invovles passing of messages; in such a system, usually, each sender actor needs to know how to address the recipient actor.

A good example of such a system is email. Actors in emails are the accounts that are hosted by email providers, and the messages are the emails.

Another good example is ActivityPub.