Hold for maintenance and temporarily inactive is the same thing. You can select a date range in which the room will not be available.
Now coming to partial availability, this concept means that if in the date range you do no have a single room available for the whole date range but two or more rooms available in fragments of that date range.
For example, a customer requests you a room from 1st to 5th. But you do not have any room free from 1st to 5th. But you have one room free from 1st to 3rd and another from 4th to 5th.
So you can give these rooms to the customer so that you do not miss a booking.
This is called Partial availability.