What is the difference between Actus Reus and Mens Rea?

Both Actus Reus and Mens Rea are elements of a crime in which both are necessary in order for the defendant to be liable. The Actus Reus is the conduct element of an offence, this is what the defendant must have been proved to have done. Meanwhile the mens rea is the mental element of the crime. This usually relates to intention or recklessness.