Facebook and PayPal struck a deal, that being that Facebook will now take PayPal as a payment option to buy Facebook credits. What are Facebook credits? They are Facebook's own monetary system for buying virtual gifts or in some games, their own credit system. 10 credits = $1 and gifts are usually 10 credits.

Not that too many people really use virtual gifts, but other ways to purchase are through your credit card or mobile phone. Both options have always been the standard payment options.