Theorems are a way for mathematicians to make a general mathematical statement. These statements can be used to help you solve all sorts of problems! See an introductions to theorems with this tutorial.
The Pythagorean theorem is a very popular theorem that shows a special relationship between the sides of a right triangle. In this tutorial, you'll get introduced to the Pythagorean theorem and see how it's used to solve for a missing length on a right triangle!