What does second in command do?

Answer 1

A Second Chef is actually the Sous Chef, who is second in command of the kitchen. Generally this position has responsibilities that include, but are not limited to the day-to-day running of the kitchen, standing in for the Executive Chef when they are unavailable, scheduling, training, and overseeing and insurance of a smooth running service kitchen. They need to know how to plan a menu, have a firm grip on food and labor cost, sanitation, purchasing, equipment, and of course, proper food preparation and storage.

Answer 2

Second-in-Command, pretty much, just repeats whatever the Captain says, but also makes sure that the Captain is alright as well. As in, the Captain isn't losing it or saying the wrong command or misleading the crew to chaos, etc.

Answer

The second in command of a warship is called the executive officer ('XO') or first lieutenant. In the Royal Navy, if the commanding officer of a warship holds the rank of captain (e.g. of an aircraft carrier), then the executive officer normally holds the rank of commander, and is known as 'the commander', rather than first lieutenant.

The executive officer is responsible for the discipline of the ship's company (the 'crew' of a warship) and for the day-to-day running of the warship.