Thunder, as a pressurized sound wave, can hurt your ears, scare children and animals, and set off some car alarms. Since it is caused by the rapid heating of air produced by a nearby lightning...
It transmits the sound of lightning in every direction. Thus, one can measure the distance to the lightning source by noting the time difference between seeing and hearing lightning.
A thunder bolt is simply an incorrect name for a lightning bolt. And, since lightning carries much more energy than thunder, the "thunderbolt" is NOT weaker than thunder.