Schur functions are a special class of symmetric functions that play a significant role in combinatorics and representation theory. They are indexed by partitions, which are ways of writing a number as a sum of positive integers. Schur functions can be expressed in terms of Young tableaux, which are combinatorial objects that help visualize the structure of these functions. These functions are important because they form a basis for the space of symmetric functions, meaning any symmetric function can be expressed as a combination of Schur functions. Additionally, Schur functions are closely related to character theory in group representations, providing insights into the representation of symmetric groups and other algebraic structures.