A more thorough explanation:

Legal impossibility refers to a situation where a person cannot be held responsible for not fulfilling a contract or committing a crime because it was impossible for them to do so. There are different types of legal impossibility:

Factual impossibility occurs when the illegal act cannot physically be accomplished. For example, trying to pick an empty pocket. Factual impossibility is not a defense to the crime of attempt.

Legal impossibility occurs when what the defendant intended to do is not illegal, even though the defendant might have believed that they were committing a crime. For example, if a person goes hunting while erroneously believing that it is not hunting season. This type of legal impossibility is a defense to the crimes of attempt, conspiracy, and solicitation.

Objective impossibility occurs due to the nature of the performance and not to the inability of the individual promisor.

Subjective impossibility occurs wholly due to the inability of the individual promisor and not to the nature of the performance.

Supervening impossibility arises after the formation of a contract but before the time when the promisor's performance is due, and arising because of facts that the promisor had no reason to anticipate and did not contribute to the occurrence of.

For example, if a person agrees to deliver a package to a client, but a natural disaster occurs that makes it impossible for them to do so, they cannot be held responsible for not fulfilling the contract. This is because the natural disaster was a supervening impossibility that they could not have anticipated or prevented.