A cook prepares and cooks food for others, either in a large kitchen under a master cook, or individually in an eatery. Many cooks join the military as the pay is better, after basic training very few see combat, or even the front lines, but they do accompany forces to provide meals.
Employed by an estate or military force to routinely and repeatedly cook food multiple times a day, in most cases it is a seven days a week role.
While players are generally free to select a citizen role as a background, they should check with the Dungeon Master to make sure it fits within the local area, other party members and does not conflict with the intended adventure.
Citizens have proficiencies in weapons and armour relative to their type and region, so it is not included in the above information, and players do not gain any proficiencies from choosing a citizen background.