Maine Revised Statute Title 17-A, §353 explains a person is guilty of the crime if
The person obtains or exercises unauthorized control over the property of another with intent to deprive the other person of the property.
To prove theft, the prosecutor must prove that you exercised unauthorized control over the thing allegedly stolen. The statute defines "exercises unauthorized control" as an act that
includes but is not limited to conduct formerly defined or known as common law larceny by trespassory taking, larceny by conversion, larceny by bailee and embezzlement.
Unauthorized control is not the only means theft is committed, but can be committed via deception, extortion, and unauthorized use.