A container class is a class that is used to hold objects in memory or external storage.
A container class acts as a generic holder.
A container class has a predefined behavior and a wellknown interface.
A container class is a supporting class whose purpose is to hide the topology used for maintaining the list of objects in memory.
When a container class contains a group of mixed objects, the container is called a heterogeneous container;
when the container is holding a group of objects that are all the same, the container is called a homogeneous container.