Executive officer (also known as Second in Command, Second in Charge, 2IC, Vice Commander, Deputy Commander or simply as XO) is a title used to describe a position or role within an organisation which is usually the second highest link in a Chain of Command.
The executive officer is a term used to describe the officer or rank directly inferior to a commanding officer. Typically a 2IC of a unit will hold the rank of Lieutenant. Similarly, Lieutenant-Colonel literally takes the meaning of "Second in Charge after a Colonel". Smaller units and unit sub-structures may also have command positions of 2IC, usually held by Sergeant or Corporal ranks.
This is adapted to many different formats across continents, nations and organisations. Typically 2ICs will organise the logistics and aid in the decisions and preparation of their respective commanders. This can involve checking Equipment, Health and Status, and overall capabilities of their subordinates.
When military units were implemented in-game, second in command of the military unit was declared as 2nd commander and is just behind the unit commander. All 2nd Commanders have to had Commander military rank.
Various companies and organisations will have Vice positions, which essentially provide support and aid for their respective superiors.
Various countries throughout the New World have Vice or Deputy positions. This may involve being second in command of a country, as a Vice president, or Deputy Prime Minister. It may also be second in command to a Minister as well, as many of these positions throughout the eWorld have deputies, vice ministers, or other 2IC positions.