Does wireless networking revolve around only one host transmitting at a time??

In my telecommunication textbook, it says that media access control is based completely around only one host transmitting on the network at a time. As I have understood this, this means that I host, say computer A, is transmitting signals back to the router and to the Internet at one single moment in time. When it is finished transmitting, computer B for example will then be able to transmit.

This is what I have interpreted from what has been written in my textbook. What I don’t understand is how this can be possible. It says that all other hosts simply wait while one hostess transmitting. If this was the case, wouldn’t the Internet be an incredibly slow place? Perhaps I am not understanding or comprehending the gravity of how truly quickly wireless signals are transmitted. Supposedly, Wi-Fi signal is radio, so I would assume that’s very fast. That’s basically lightspeed in compared to the way humans with each other.