Ahh.. you're crossing over to "the dark side"... ;) Most likely the course sheet (or prizelist) will clarify the classes into "tables" (the official classification for the rules).
Table II, Section 2(b)- "timed first jump off". Your basic jumper course. You do your round. If you have a fault you're excused. If you're clear you wait for the buzzer (you can stop, just can't leave) and then you have 45 sec to cross the timer to your first jump of the jump off.
Table II, Section 2(c) "power and speed". Somewhere in your course is a designated finish line. You begin your course (power phase) and if you are clear you -without stopping- begin the speed phase. So it's like one giant course but you start off more carefully and somewhere in the middle you should pick up the pace a bit. If you are not clear in your power phase they buzz you out and you leave the ring without doing the speed phase.
Table II, Section 2(a) -aka 'timed first round'. All you do is your first round, and there is no jump off unless there is a tie for first.
Table V, Section 1- "Optimum Time"- You are given a certain time the course should be completed in. You get faults if you are over the time allowed (along with knock downs). I feel like you can get faults for doing it too quickly too... it's been so long since I"ve done an Optimum Time round!
Hope that helps! Good luck!