It means that Facebook will use another medium of exchange instead of traditional credit card system to boost payment security and speed.
The credit card system can't support a lot of transactions per second. In order for Facebook to support mass payments, it needs to add a crypto to its system.
Cause crypto is both secure and private. If facebook tried to do it with its own centralized database, then if Facebook system got hacked, they will lose control of the system and the funds.
But if they use a crypto, it will make the system more secure and decentralized. It will be more acceptable to the general public.
When Facebook adds that system, they will be able to support a lot of things that it can't support now.
It can support direct buy and sell of products within the Facebook interface. People will be able to tip their favorite entertainers easily.