Gottlob Frege argues in Uber Sinn und Bedeutung that every intuitively meaningful expression has a sense. He characterises the main ingredient of sense as a ‘mode of presentation’ of at most one thing, namely the referent. Theoretical development of sense and reference has been a fundamental task for the philosophy of language. In this article I will reconstruct Frege’s motivation for the distinction between sense and reference (section 2). I will then go on to discuss how the distinction can be applied to predicates, sentences and context- dependent expressions (section 3). The final section 4 shows how discussions of Frege’s theory lead to important proposals in semantics.