So what happens when 2 people in the same room want to use the internet?
Same thing happens with wireless. That's what protocols are for.
Most people seem to have forgotten that the original use for 802.11 was allowing computers to communicate using infra-red light. This interface was common on 90s laptops and was the reason for WiFi having its 'ad hoc' mode of operation that didn't use an access point as such.