Before switches, networks based on hubs data could only allow transmission in one direction at a time, this was called half-duplex. By using a switch this restriction is removed; full-duplex communication is maintained and the network is collision free. This means that data can now be transmitted in both directions at the same time.
Before switches, networks based on hubs were limited to half-duplex communication, where data could only be transmitted in one direction at a time. The introduction of switches removes this limitation, enabling full-duplex communication and eliminating collisions.