A First Officer also known as a co pilot is a trained commercial pilot who works alongside the Captain to operate the flight safely. They sit in the right seat of the cockpit and act as the second in command. While both Captain and First Officer take part in flying navigation communication safety checks and other flight tasks the First Officer supports and assists rather than holds full authority.
Operates the aircraft during parts of flight (take off landing cruise).
Monitors flight instruments fuel weather navigation systems engine performance.
Communicates with Air Traffic Control (ATC) cabin crew and ground staff.
Assists in route planning flight preparation safety checklists and standard operating procedures (SOPs).
In emergencies supports the Captain and can take over if needed.
The Captain is the Pilot in Command i.e. the final authority for the flight's safety operations and decisions.
They lead the crew, make critical decisions before during and after the flight including planning navigation emergency handling.
Whereas the First Officer assists and shares many duties, the Captain remains legally responsible for what happens on board.
Even though rank and authority differ smooth and safe flight operations depend on cooperation. The First Officer isn't just an assistant they actively fly monitor systems communicate and support in emergencies. When both Captain and First Officer work well together the flight becomes safe efficient and comfortable for everyone.