C++ Containers
The C++ Containers (vectors, lists, etc.) are
  generic vessels capable of holding many different types of data. For
  example, the following statement creates a 
vector of integers:
  
vector<int> v;
Containers can hold standard objects (like the
int in the above example) as well as custom objects,
as long as the objects in the container meet a few requirements:
  
    - The object must have a default constructor,
- an accessible destructor, and
- an accessible assignment operator.
When describing the functions associated with these various
  containers, this website defines the word 
TYPE to be
  the object type that the container holds. For example, in the above
  statement, 
TYPE would be 
int.
  Similarily, when referring to containers associated with pairs of
  data (
map for example)
  
key_type and 
value_type are used to
  refer to the key and value types for that container.