Throughout the history of mathematics, contemporary mathematics included, mathematicians have re-proved theorems by means of different proofs. The Pythagorean theorem is a clear example of this mathematical practice: more than 350 proofs have been documented. During the last decades, several philosophers of mathematics have argued that there is a distinction between explanatory and non-explanatory proofs. The idea is that, while all proofs of theorem T show that T is true, some proofs also reveal why T is true. The aim of this project is to increase our insight into what makes explanatory proofs important. What is gained by having an explanatory proof? What does the explanatory value of explanatory proofs consist in? These questions are addressed in this project.