The people in your fort are called survivors. Survivors exist to accomplish various missions, which serve to acquire resources for your fort, make it safer, or otherwise increase your fort's chances of continued existence. Survivors not assigned to a specific mission remain inside the fort on Guard Duty, keeping other survivors safe from marauding zombies.
Each survivor needs a house to live in, and will consume 1 unit of food per day. Every survivor is rated in five different skills, has a happiness level from 0-100, can equip one weapon and one nonweapon, and can have up to 4 perks.