Libra isn't Facebook's only big leap into the payment world. The social media giant has unveiled Facebook Pay, its bid at simplifying both purchases and money transfers. Once you've set a payment method, it's theoretically quick and easy to buy tickets, shop on Marketplace, contribute to fundraisers or cover your share of last night's pizza. You can set it up on an app-by-app basis, but Facebook also lets you set it up across apps -- a one-time setup could make it useful across Facebook's ecosystem. The core app and Messenger will support Pay in the US this week, while Instagram, WhatsApp and more countries are in the pipeline.