The people of your kingdom, your settlers, will perform a variety of tasks for you as follows.
Settlers assigned to work yards are workers. They gather or produce goods and carry them to the nearest storehouse, and repeat, until one or more inputs they need are no longer available. For example, stonecutter will continue to gather stone until the stone pile is exhausted. A baker will continue to make bread so long as water and flour are available.
Settlers assigned to constructor special buildings follow your orders to construct buildings. When you order a new building, the resources need to construct the building are gathered at the storehouse nearest the location. Once the resources are present the constructor moves to the storehouse, picks up the resources, carries them to the building site, and constructs the building.
These settlers are assigned to storehouses and they attempt to fulfill the demand signals from work yards and other locations in your kingdom. For example, if you have a butchery operating, it requires animals to make fancy food. An operating butchery creates demand for animals. Your carriers will get the demand signal from the operating butchery and attempt to move animals from storehouses holding them to the storehouse closest to the butchery.
This is a special unit that commands armies. You begin each map with one basic general. You may unlock the ability to hire additional generals with better abilities at the Tavern. Better generals can improve some aspect of an army's fighting ability.
There are five types of soldiers that you can train and assign to armies. All soldiers can be trained at the stronghold once that special building is fully upgraded. In addition, some soldiers can be hired at the Tavern. Soldiers in armies are used to attack sectors and fight enemy armies.
There are three types of cleric that you can train at an upgraded church. Clerics can be sent to monasteries to do technology research, they can be used to overtake neutral sectors, and they can bolster the defense of your fortified sectors.
There are three types of trader that you can train at an upgraded export office. Traders can be sent to the trade board to establish trade routes. They can exchange goods and coins at port and marketplace sectors. They can be used to overtake neutral sectors.