Apple’s Roadside Assistance feature is a way for iPhone owners to call for help when they have issues with their cars requiring professional help when they’re located in an area that doesn’t have a cellular or Wi-Fi connection. To do this, Apple uses a network of satellites, the same way that OnStar does for its own roadside assistance services. In Apple’s implementation, it’s text-based with generic messages to choose from so as to utilize as little bandwidth as possible.
A satellite orbits the Earth and serves as a relay to transmit radio signals across large coverage areas, like entire countries. In practice, this has most prominently been used for television and radio signals, both behind the scenes and direct to consumers via the likes of DirecTV, Dish Network, and Sirius XM, but also satellite phones, OnStar, and similar systems to provide some kind of communications link just about anywhere. It’s why SiriusXM’s satellite radio service has long been popular with long-haul truck drivers, and also why satellite TV and to an extent satellite internet are go-to solutions in areas too remote for cable or fiber connections.