It doesn’t.
Compression and extension are the terms you need to use. Then, think about how the spindle travels on the control arms. The spindle travels in an arc, so, that’s where the camber change comes from.
As the suspension is compressed, the spindle travels up on its arc, tilting the top of the tire toward the car- negative camber.
As the suspension is extended, the spindle arcs down, tilting the bottom of the tire toward the car, and the top away- positive camber.
Of course what the camber actually is depends on where your ride height is set at and what your camber is at that height. That’s one reason lowering the ride height helps suspension geometry and handling. You want the camber to go more negative with compression, it helps keep your tire contact patch parallel with the road when cornering. The lower the car sits, the faster you gain negative camber on compression. At the stock ride height the camber curve isn’t great. If the car is lowered so the control arms are close to parallel, you get negative camber gain with compression.
Hard cornering causes the camber to go more negative. Negative camber gain on the camber curve. On the outside wheel anyway, which is the one that matters.
