Euclidean geometry is a system in mathematics. People think Euclid was the first person who described it; therefore, it bears his name. He first described it in his textbook "Elements". The book was the first systematic discussion of geometry as it was known at the time. In the book, Euclid first assumes a few axioms. These form the base for later work. They are intuitively clear. Starting from those axioms, other theorems can be proven.