Just to expand on
Maximum's reply: It is not just the Shutlle, but
all rocket launches which follow the same procedure. The giant pads at KSC, Cape Canaveral, Korou, etc, are fixed in one place. As no two launch trajectories are exactly the same, every flight has to be orientated to it's correct inclination after lift off.
Even the "circular" cross-sectioned rockets have X,Y,Z axes for guidance and orientation purposes, although it's not easy to see this at first view. The mighty Saturns followed a
Roll Program after clearing the tower but not through such a great angle as the Shuttle and therefore not as obvious to the casual observer. Next time you have the oportunity to view an unmanned launch, watch carefully and you will notice the craft rotate about its longitudinal axis shortly after lift off.
Shuttle steering is achieved by a combination of the aero-surfaces and the gimballing of the booster and main engine nozzles, depending on the exact point along the flight path. There was a slightly more detailed answer
here last time this one came up. Hope this helps.