Definitions of good behavior
in some jurisdictions, if an offender (=someone who has committed a crime) behaves well during a fixed period of time, he or she might have to serve less time in prison
He received time off from his prison sentence for good behavior.
under the US Constitution, justices (=US Supreme Court judges) "shall hold their offices during good Behavior". The term "good behavior" means that they can serve as justices for the rest of their lives unless they resign, retire, or are impeached and convicted by Congress.
Wrongful acts by judges constitute a violation of "good behavior" deserving impeachment.