A more thorough explanation:

Compulsion is the act of forcing someone to do something or the state of being forced to do something. It can be physical force, but it can also take other forms. Even if someone is forced to do something, it is not a defense for any crime committed through yielding to it. There are different types of compulsion, such as obedience to orders, martial coercion, duress per minas, and necessity.

Compulsion can also refer to an uncontrollable urge or inclination to do something. It is like a strong feeling that you cannot resist.

Objective necessity or duress is another meaning of compulsion. It is when someone is forced to do something because they have no other choice.

• He felt a compulsion to check his phone every five minutes, even though he knew he should be studying.
• The kidnapper used compulsion to force the victim to give him the money.
• The soldier followed orders out of compulsion, even though he knew it was wrong.

The first example shows how compulsion can be an uncontrollable urge or inclination. The second example illustrates how compulsion can be physical force. The third example demonstrates how compulsion can be obedience to orders.