As others have said the videos give you instructions and you suffer along to some great footage.
I've started using them along with Trainer road which makes them much more interactive as it gives you a power meter to cycle at, (Calculated on the power curve of your turbo trainer / Witchcraft). Trainer road needs a subscription, and an Ant+ USB stick and cadence/speed sensors, (but I have that for my Garmin anyway), but it does take the perceived suffer scale to another level.
I'm finding the two together are really helping keep me motivated on the trainer during the dark winter evenings, looking forward to seeing the benefit in the spring I hope.