A special class of scheduling problems is studied in this paper, named Hybrid Flowshop, n jobs have to be performed in a shop and each of them has the same routing (so this is a flowshop). A job consists in k different operations. A set of machines are able to perform each operation and this set is called a stage. So when a job consists in two operations, there are two stages in the shop. After introducing the scheduling generalities, we define our preocupations and we propose a notation in order to identify precisely and rapidly a problem. Then a state of the art is proposed and presented in two parts. The first one is dedicated to the 2-stage hybrid flowshops and the second to the general case of the k-stage. Then a summary puts to the fore that many problems remain unsolved.