PayPal Express - Basically you have to pay using your PayPal Account (Personal or Business) - the person you pay is charged a transaction processing fee - you can use your account balance, bank account or a card as your funding source.
PayPal Goods and Services - You would use the Send Money feature from within your PayPal Account (Personal or Business) and choose Goods and Services - the person you pay is charged a transaction processing fee - you can use your account balance, bank account or a card as your funding source.
Mass Pay - This a bit different, Mass Payment is an easy and efficient way to send money to a group. With Mass Payment, you can send money to up to 5,000 people at once, you must have a Business Account. You can learn more here.
