we set fixed levels of certain currents and voltage in a transistor. now these values of current and voltage define the point at which the transistor operates. this point is known as Q point or operating point or Quiescent point...
Q-point is the point in design of transistor circuits where, under certin conditions, the AC and DC load lines intersect. By designing your circuit to have the DC load line half way on the AC loadline, it allows for a full AC voltage swing on the input. If the Q point is not in the middle of the loadline, clipping will occur.