This book is based on courses taught to graduate students at The Institute of Mathematical Sciences, Chennai, and undergraduates of Chennai Mathematical Institute. It presents important combinatorial ideas that underpin contemporary research in representation theory in their simplest setting: the representation theory of symmetric groups, the theory of symmetric functions and the polynomial representation theory of general linear groups. Readers who have a knowledge of algebra at the level of Artin's book [1] (undergraduate honours level) should find this book quite easy to read. However, Artin's book is not a strict pre-requisite for reading this book. A good understanding of linear algebra and the definitions of groups, rings and modules will suffice.