GTSboy answered that. There is a single plate lockup clutch in the torque converter, it's job is to obviously lock up the torque converter, to make it direct drive, like a manual clutch.
There are also many clutches in the gearbox for the gears, and a band (like a drum brake) to slow the car when you back off. If yours is revving right out on slip it will be the gear clutch which has worn. If it only revs out onto the stall converter speed, it will be the lockup clutch that is faulty.