Let’s start off with a swing-arm suspension system. This is where the arms are pivoted at or near the centre of the car.
When the wheel passes over an obstacle on the road (like this red rock), the wheel rises, pivoting around the inner point. You can see that the camber of the wheel (the angle it makes to the vertical) changes a great deal - that’s one of the negatives of this type of suspension system when being used on most (but not all) types of vehicles.
The length of the arm around which the wheel is pivoting (shown here in purple, and drawn to the centre of the wheel) is, as you’d expect, called the ‘swing-arm length’. The longer the swing-arm, the less the camber of the wheel changes for a given size of bump.
In fact, to minimise camber change, this 1960s Honda 1300 front-wheel drive used a rear suspension comprising swing-axles pivoted from the opposite sides of the car.
However, in many cases, less camber change is desired than can be achieved even with very long swing-arms. The trick is to swap to a different design of suspension, like the double wishbones shown here. The disadvantage is that the number of pivots has risen from one to four, and the number of arms has doubled (both significant deficiencies in, for example, ultra light-weight vehicles). But one benefit is that the wheel can remain vertical during its suspension movement – that is, the camber doesn’t change with up/down suspension movement.