Area of control
Control is one of the most important parts of the Far Wilds. Each player has an area of control, usually determined by your Buildings. Buildings give you control over any space they can see. If two players control given space (for example both have Buildings that can see space) that space is uncontrolled.
Control doesn't give you vision of spaces that you control, so it is possible that you control, but can't see some spaces.
If you control a space that contains a Flux Well you gain control of that Flux Well.
You can see here that you control the blue area around your two buildings. Your Bone Fortress has vision 2 so has a larger radius of control then your Grove. Your Astridian Forum is also a building but it has vision of zero so doesn't expand your area of control..
When two players have buildings that can see the same space. That space is considered contested and isn't under anyone's control.
In this example the enemy just placed an Earthworks and so we lost control of the center Flux Well. Note that even though our Altar of Ix and Bone Fortress can both see the center point it only takes one enemy building to make the space contested.
Any uncontrolled building (i.e. buildings without a controller, marked with white color) also have area of "control" that prevents area from being controlled, also there are cards like Desolation Totem that prevent an area from being controlled. Such areas are always uncontrolled and considered contested until any Entities that cause prevent control are removed.
Control uncontrolled areas
Some cards (i.e. Bronze Statue) says "control spaces that aren't controlled by anyone else". That gives you control of spaces that have no controller but not contested area. If two players have card with such a property in play, any space that would be controlled by both players is considered contested and is uncontrolled.
Control in Team Games
In team games, the most recently placed building/effect controls the spaces specified, regardless of other team member's buildings.