system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why do large commercial planes have two steering wheels and two pilots?

How exactly does it help to have two people steer a plane at the same  time?
gpt
Virtually all multi-seat planes have two sets of steering wheels; even the lowly Cessna 172.

Note that the controls *cannot* be used independently: moving one set of controls will also move the other set.

With those preliminary concepts aside, the basic answers are: redundancy and specialization. The co-pilot might perform special tasks to take some work off the pilot (radio communication, monitoring certain instruments, etc).