Drift is when minor tracking inaccuracies build on top of each other over time, and the tracked position and real position are separated (drifted apart). This is a problem with acceleration and velocity/intertia based sensors more than “positional” sensors, although drift can also be introduced through errors in extrapolation, interpolation, and noise reduction.

Many headsets use a combination of sensors, relying on inertial sensors for their fast-update times and positional sensors to constantly correct for the drift/innacuracy of the inertial sensor.