Official Aviation Definition
A taxiway is a paved path on an airport established for aircraft to taxi between runways, aprons, passenger terminals, and maintenance hangars. Taxiways are marked with yellow centerlines and edge markings and illuminated by blue edge lighting or green centerline lights.
In Simple Words
The roadways and connecting lanes that airplanes drive on between the gate and the runway.
Real-World Flight Example
The controller cleared the aircraft to taxi to Runway 04 via Taxiway Alpha, Bravo, and hold short of Runway 22.