Ideally, should buttons’ state represent current or desired behavior? [duplicate]

Ideally, should buttons' icons or state (button clicked or not clicked) represent current or desired behavior? On Android, certain checkbox options may also have a description (below the name of the option itself) - should the description describe: 1. the new behavior that will apply when (un)checking the option, or 2. the behavior when the option is checked (with the implication that the opposite behavior will apply when unchecked)? Thanks.