Clutches are designed to slip when engaged so the vehicle doesn’t jerk or lurch forward when starting out. Once the clutch pedal is fully released, the clutch should hold firm and not chatter, slip or catch, and provide a solid coupling between the engine and transmission. If it doesn’t, something is wrong and needs to be investigated.
Slipping or chatter are most noticeable when the engine is under load, as when the vehicle is lugging at low speed in a high gear, when driving up a hill, when accelerating to pass another vehicle, or when towing a trailer.
Slippage increases friction and produces heat, which leads to hot spots on the pressure plate. The hotter the clutch gets, the less able it is to maintain its grip, and the more it slips. The vicious cycle that results can burn the clutch facings and damage the flywheel and pressure plate.