In the programming world, the word aggregate relates to a collection of data objects that form a data type. In other words, an aggregate object is one which contains other objects. For example, A car consists of several parts, like the engine, transmission, brakes, gearbox, etc.
It is interesting how the word aggregate in the normal sense and from a programming perspective means the same thing.
In programming, aggregation is a type of object composition where not all the containing objects should be destroyed when the owning object is destroyed.