The aim of this paper is to give motivations for the development of operational semantics in membrane computing, and to survey existing proposals. In particular, the definitions are compared of three operational semantics available in the literature, namely a semantics proposed by Andrei, Ciobanu and Lucanu, another proposed by Busi, and another one proposed by the authors of the present paper. These definitions are different since they are given with different aims. However, we show that there is an operational correspondence among the three.