A more thorough explanation:

Actus reus refers to the physical actions or omissions that make up the elements of a crime as required by law. It includes only voluntary affirmative acts or omissions that cause a criminal result. In other words, it is the guilty act that must be proven in order to establish criminal liability.

For example, if a thief points a gun at someone and demands their money, the act of pointing the gun is the actus reus. However, if the thief accidentally drops the gun and it goes off, injuring someone, this would not satisfy the actus reus requirement because it was an involuntary act.

It is important to note that an omission can also satisfy the actus reus requirement if the individual had a duty to act and failed to do so. This duty can arise from a statute, contract, special relationship, voluntary assumption of care, or creation of the risk.

Overall, actus reus is the physical element of a crime that must be proven in order to establish criminal liability.