What is the main operational difference between a wet clutch and a dry clutch in a motorcycle?

1. A wet clutch can only be used on two-stroke engines
2. A dry clutch must be lubricated with grease every 1,000 kilometers
3. A wet clutch requires special high-pressure air injection to stay cool
4. A wet clutch is bathed in engine oil to dissipate heat, while a dry clutch runs in open air and is noisier