Usually the ambient properties are visual properties, like ForeColor or Font. Typically the ambient inheritance is only down-stream, which means children are inheriting ambient properties from their parent elements, and not the other way.
For instance, lets consider element A, with a ForeColor property, element B, child of A, and element C, child of B. B inherits the ForeColor from A, and C inherits the ForeColor from B.
In this case when we change the ForeColor of A, the ForeColor of both B and C are changed in cascade. But if we set the value of B's ForeColor, explicitly to a different value, it will no longer inherit the ForeColor from A, instead it will have it's own value. And this is exactly what we wanted. We want to be able to set the same properties for a large amount of child elements, but we also want to give the flexibility of setting each child's property separately to a different value.
In PlusSuite many controls use the ambient properties. For example, in a PlusShortcutBar each page inherits some properties from the parent bar and each page item inherits some properties from the parent page. The same for the PlusListBox and it's child PlusListBoxItems. All ambient properties have a Reset method. For example, for a ForeColor property you will find a ResetForeColor() method. This method will remove the explicitly set value and will make the element become ambient again.
As a way of speaking, when we say "the property X of element Y is ambient" we mean that the element Y inherits the property X from its parent, also known as Ambient Parent. If the element Y has its value explicitly set, we say that "the property X of element Y is not ambient".
Ambient properties offer an extraordinary flexibility and PlusSuite takes advantage of this fact.
See Also
General Concepts:Drop-down Controls | General Concepts:Visual Style