Yeah. It‘s the framework which does pretty much all of the interesting technical work, if I may say so. It does the communication with other phones and determin

Yeah. It‘s the framework which does pretty much all of the interesting technical work, if I may say so. It does the communication with other phones and determines if there was a contact and generates, stores and maintains the tokens and given the server data figures out matches and so on. It has a tiny, simple to use API on top. It was jointly developed by Apple and Google. For free.