why api code example

Example 1: what is api

API : Application Programming Interface
An api is a particular set of rules and specifications that programs can 
follow to communicate with each other .
The end user sends request , API executes instructions then get the data 
from the server and responds to the user.

Example 2: why api

It verifies all the functional paths 
of the system under test very effectively.
It provides the most stable interface.
It is easier to maintain and 
provides fast feedback.