Rationality is nothing but status of being reasonable, sensible, and having good sense of judgment.
Rationality implies the conformity of one's beliefs with one's reasons to believe, or of one's actions with one's reasons for action.
It is concerned with expected actions and results depending upon what the agent has perceived.
Performing actions with the aim of obtaining useful information is an important part of rationality.
A rational agent is an agent which has clear preferences and models uncertainty via expected values.
A rational agent can be anything that makes decisions, typically a person, firm, machine, or software.
A rational agent always performs right action, where the right action means the action that causes the agent to be most successful in the given percept sequence.
Rational agent is capable of taking best possible action in any situation.
Example of rational action performed by any intelligent agent:
Automated Taxi Driver:
Performance Measure: Safe, fast, legal, comfortable trip, maximize profits.
Environment: Roads, other traffic, customers.
Actuators: Steering wheel, accelerator, brake, signal, horn.
Sensors: Cameras, sonar, speedometer, GPS, odometer, engine sensors, keyboard.