Twisted groupoid C*-algebras were introduced by Renault in 1980 and are a generalisation of twisted group C*-algebras, which are the C*-algebraic analogue of twisted group rings. Through the work of Renault and more recently of Li, it has emerged that every simple classifiable C*-algebra can be realised as a twisted groupoid C*-algebra, a result that has led to increased interest in the structure of these C*-algebras. In this talk I will describe the construction of reduced twisted C*-algebras of Hausdorff étale groupoids. I will then discuss my recent preprint in which I prove a uniqueness theorem for these algebras and use this to characterise simplicity in the case where the groupoid is effective.