Representation theory is the study of the basic symmetries of mathematics and physics. Recently, it has known some spectacular developments, thanks to the introduction of new technics such as categorical representations or parity sheaves. The continued development of the subject has motivated a trimester in representation theory at the IHP that will take place in 2020 from January to March. This program will begin with an introductory conference. It will consist of 6 mini-courses on the main topics (categorifications and quantum groups, quiver varieties, character varieties, geometric representation theory). It is devoted to younger researchers, but also to senior ones in order to promote the discussions between young mathematicians and seniors.