I would assume that you are asking in the context of variance analysis.
The standard hours are the hours that each unit is budgeted to take.
The budgeted hours are the total number of hours that they expect to use.
The actual hours are the hours that they actually end up taking, which might be more or less that the hours they budgeted/expected to take.
I do explain all of this in my free lectures. The lectures are a complete free course for Paper PM and cover everything needed to be able to pass the exam well.