This document provides an overview of irrational numbers and surds for a GCSE maths class. It begins by defining rational and irrational numbers, then discusses surds and how to manipulate them within expressions and fractions. Examples are provided of simplifying surds, expanding expressions involving surds, rationalizing denominators, and solving worksheet questions involving surds. The document aims to help students understand the difference between rational and irrational numbers and how to work with surds.