https://www.theverge.com/2017/12/4/16734154/apple-pay-cash-ios-iphone-update-available-now

Apple was forced to release iOS 11.2 on Saturday, which was a little earlier than planned, due to a software bug. Now, Apple Pay Cash — one of the marquee features of the update — is being activated for users.

Apple Pay Cash lets users send and receive money directly though iMessages, similar to Venmo or Square Cash. Money that people send you will live on a digital Apple Pay Cash card in the Wallet app, which users can spend anywhere that Apple Pay is accepted, or send to other people.