Final answer:
In the example 'the gun was found under the seat,' the gun is the object that receives the action of being found. It is important to distinguish the subject from the object in sentence construction.
Step-by-step explanation:
The phrase 'receives the action' typically refers to the object in a sentence, which is the entity that the action is being done to or acted upon. In the given example 'the gun was found under the seat,' 'the gun' is the object that received the action of being found. In English grammar, when identifying the parts of a sentence, the subject is the doer of the action, and the object is the receiver of the action.