A provider that I am going to see next week accepts credit card payments using paypal. What is paypal and how do I use them? Thank you for your help

If you don't mind a paper trail it's fast and easy. But I am a little confused that providers are still gambling with paypals terms of service and the chance of freezing the account for several months. Paypal doesn't accept adult transactions anymore and if they find out they freeze the merchants account.