The difference between Actor and Agent

Actor as a noun:

A person who performs in a theatrical play or film.

Actor as a noun:

One who acts; a doer.

Actor as a noun:

One who takes part in a situation.

Actor as a noun (legal):

An advocate or proctor in civil courts or causes.

Actor as a noun (legal):

One who institutes a suit; plaintiff or complainant.

Actor as a noun (policy debate):

One who enacts a certain policy action.

Actor as a noun (software engineering):

The entity that performs a role (in use case analysis).

Agent as a noun:

One who exerts power, or has the power to act

Agent as a noun:

One who acts for, or in the place of, another (the principal), by authority from him/her; someone entrusted to do the business of another

Agent as a noun:

A person who looks for work for another person

Agent as a noun:

Someone who works for an intelligence agency

Agent as a noun:

An active power or cause or substance; something which has the power to produce an effect

Agent as a noun (computing):

In the client-server model, the part of the system that performs information preparation and exchange on behalf of a client or server. Especially in the phrase “intelligent agent” it implies some kind of autonomous process which can communicate with other agents to perform some collective task on behalf of one or more humans.

Agent as a noun (grammar):

The participant of a situation that carries out the action in this situation, e.g. "the boy" in the sentences "The boy kicked the ball" and "The ball was kicked by the boy".