### Theory:

Let us first consider the representation given below.

The image given above is a cipher circle. Here $$A \rightarrow D$$, $$B \rightarrow E$$, and so on.

When represented as a function, the cipher circle is both one - one and onto.

Bijection:
A function that in both one - one and onto is a bijection.

Since the bijection function is one - one and onto, it is also called one - one correspondence.

Also, a bijective function is both surjective and injective.