The document discusses identifying the sides of right triangles for use with the Pythagorean theorem. It explains that the theorem only applies to right triangles, which have one 90 degree angle. The sides of a right triangle are labeled A, B, and C. Side C is always the longest side and is opposite the 90 degree angle. Side C is called the hypotenuse. The document provides examples of labeling right triangles regardless of their orientation and emphasizes correctly identifying the hypotenuse.