What is c ?

Answer 1

As you have completed the sololearn C course, I think you already know the answer. If not, you can re-read the lessons as often as you like.

https://www.sololearn.com/Course/C/?ref=app

Answer 2

a programming language :)

Answer 3

C is a general purpose, simple programming language that works closely with the memory. It is one of the most popular language that still used in each programming contest and taught by institutions before entering programming domain.