In The Extraction you are in an bunker and need to find resources outside of your bunker. The bunker will need maintenance inorder to stay in good condition. You may encounter factions or other survivors out in the world some might be hostile. You need to mentain your needs, repair the bunker, repair broken down vehicles and so on. Different factions have different goals, morales and strength. You don't need to do this alone and you can find other people to recruit.