The major difference between these kinds of punishments is that the first two are alternatives to prison while the third is something that can happen after a person has been in prison.
Probation and intermediate punishments are punishments that are less harsh than being sent to prison. Probation is the least severe punishment of this sort. When a person is sentenced to probation, they are only lightly supervised. They must typically agree to a variety of conditions such as prohibitions on consuming alcohol or on associating with known criminals. However, they are not under constant surveillance. Intermediate punishments are more severe than probation, but not as punitive as incarceration. This can include things like electronic surveillance of the convict. Another form of this would come when a judge orders a convict to undergo drug rehabilitation and closely monitors the convict’s performance.
By contrast, parole is something that happens while a person is still under a prison sentence. The individual is released from prison without serving the entire sentence. However, they must obey certain conditions and are liable to be sent back to prison if they violate the terms of their parole.