When laser shows first came into existence they were performed live as a laserist would turn several knobs and switches to generate the impressive laser effects and imagery.  Not only did this enable the laserist to be a performer but no two shows were ever the same.  A laserist would feed off of an audience's energy; producing effects that they seemed to enjoy the most.
Today's laser show technology utilizes computers and sophisticated hardware to produce extremely complex laser shows that are precisely choreographed with music and other effects.  These laser shows can be pre-programmed and with a mouse click an entire laser show can be executed without an operator.
LGP and most other laser show "purists" still incorprate live performance elements to the laser display.  LGP utilizes mutiple DMX and midi based control consoles for both proramming and live performance.  Although the majority of the laser show content is pre-generated, the laserist can still interact and add effects to the show.

An old video that describes the job of a Laserist !!!