Fly.io is a platform that runs container images on hardware around the world, linked to an Anycast network with a WireGuard mesh. Users can deploy Docker containers in single-digit minutes and interact with their apps using flyctl, Fly.io's command-line interface. The platform uses WireGuard for communication between users and its infrastructure. Fly.io has faced challenges such as slow peer creation times and potential issues with UDP-only connections but continues to improve and innovate in network engineering.