newbie question, please bash me after I get my first explanation of how spinervals work.

I think i was misled on how spinervals work. I was under the impression that the video followed along with you on your trainer and you had to adjust your trainers resistance to simulate hills, mountains, etc.

How exactly do they work? do you need a specific model trainer so you can adjust to the spinerval videos?

Any input is appreciated, i've looked over their site and have yet to find an explanation on how they work. Their intro video was pointless...