If the real power (kW) and the reactive power (VARs) are flowing in the same direction, it is LAGGING. If the two are flowing in opposite directions it is LEADING. That's all you need to know.
So a generator that is producing real kw and vars is lagging. If it is absorbing vars while producing kW it is leading.
A typical induction motor is consuming kW and Vars, so it is lagging. A synchronous motor consuming kW but producing VArs is leading.