**Category theory** is a way of studying mathematics in terms of structures and relations between them. The *mother*
category theory is the theory of set and functions. Other prototypical examples are linear algebra, topology and
all the theories included in the abstract algebra.

In simple terms, a **category** consists of two parts:

- the
**objects**of the category - the
**morphisms**between the objects of the category

There are also relations between categories: a mathematcal application (functions or maps) from category-one to category-two is called functor if the relation sends objects into objects and morphisms into morphisms.