You have to have a Paypal account, and either a bank account or a credit card (Mastercard, Visa, etc.). Paypal basically allows you to manage money online and buy things online without having to transfer money and worry about card information. It's a really secure site; everyone uses it. I made one recently. It's how I got my deviantART subscription, and during the summer I'm going to improve and start doing commission work of my own.
To get the money to someone...I think they have to know your paypal account so they can send money to it. I'm not sure though.