[Gaz64]

That is a dry twin disc clutch. Works with the same principle as multiplate wet clutches in Automatics or motorcycles. The "Steels" are the driving member, the "Frictions" are the driven member.
The more plates you have, the more torque capacity the clutch has. Automatics have 6 or more plates per stack, since they need to get the torque capacity in a small package.