The Camp is your safe haven.

Here you can build and upgrade buildings you'll need to help improve your survivors' survival skills and gear, but you'll also be able to interact with other survivor groups.
 
The Council will be the main building in your base and upgrading it often will unlock new types of buildings and benefits. Along with your Council you will also want to upgrade your Storage and Mission Car so you can store more resources.

Out here in the Camp you'll also want to manage your band of survivors. Recruit more survivors, train them, give them more powerful equipment and build a Hospital so they can recover in between missions.

When things get tough, band together with friends and form a Guild to take on Challenges. You'll be able to access all social features from here as well. Make sure to give yourself a cool, unique but proper nickname.

And keep in mind to visit the Campfire now and then as you may find more Missions and rewards here.