Messenger Codes work in essentially the same manner as Snapchat codes; you simply scan the code that someone sends you to instantly connect with them. Usernames and links perform the same base function -- giving other people a quick means of finding you on Messenger. Usernames can easily be added to business cards and other physical media, as the Facebook blog announcement suggests, while links are meant to be integrated into email signatures. The new features are being made available to businesses as well as individual users, which should dovetail nicely with the company's rumored efforts to enable purchases directly through the app.