AFI is nothing but the design that you create to program your FPGA. AWS provides this service to register, query, manage, copy, and delete AFIs. Once an AFI is created, it can then be loaded on a running F1 instance. User can load multiple AFIs to a single F1 instance, and then can switch between AFIs in runtime without even rebooting it. This lets the user to quickly test and run multiple hardware accelerations in faster sequence. Hope you got an idea of AFI.