Introduction to string dualities

Recent progress in superstring theory is reviewed. It is shown how S- ,T-, and U-dualities arise in the study of string compactifications, solitons and D-branes to interrelate tring theories previously thought to be completely different. Though there are still no proofs for a number of statements, dualities provide an insight not only into string theory itself, but also into geometry and supergravity. Special attention is given to physical aspects which may escape notice in specific problems. The article is intended for a very general reader with little or no background knowledge.