Rolling the edge of the roller against the surface of the discs traps a microscopic oil film between them. The effect is rather like a car tyre aquaplaning on a wet road; the surfaces do not touch but are separated by the fluid.
However, unlike the car tyre, the variator is able to transmit power across the oil film. This is because the special long chain molecules used in traction fluid interlock with each other when the fluid is compressed, becoming highly viscous (glassy) under pressure. This means that as pressure is exerted at the contact points between the rollers and the discs, the oil resists the tendency to slide and transmits the power effectively.
