An agent is anything that can perceive its environment through sensors and acts upon that environment through effectors.
● A human agent has sensory organs such as eyes, ears, nose, tongue and skin parallel to the sensors, and other organs such as hands, legs, mouth, for effectors.
● A robotic agent replaces cameras and infrared range finders for the sensors, and various motors and actuators for effectors.
● A software agent has encoded bit strings as its programs and actions.
