There are four different types of association: bi-directional, uni-directional, Aggregation (includes Composition aggregation) and Reflexive.
From what I know:
Composition relationship is used for objects that have a has-a relationship to each other. E.g. A car has-an engine.
Whereas, aggregation is a weaker form of composition relationship in which the object doesn't take the ownership of another object. E.g. A university department has a teacher.
In association relationship, there's no concept of has a being used and the objects association is completely independent and thus, they don't belong to a certain class. E.g. you drive a car.
What does it mean that composition and aggregation are a type of association relationships? or do they stand on their own?
On some other resources I have read which state that: "Composition is a special form of association" and "Composition is a special case of association" and they are described in independent sections of their own and not in a "sub-section" of association down below it. Therefore, the confusion about how exactly it is type or sub-type of association relationship.