you picked a hard one , but here goes
horse power & torque go hand in hand , when calculating horse power torque is part of the formula , as does RPM
the ideal when looking at a graph / power curve from a dyno ( rolling road is what i think you call it ) is to make high torque at low rpm
when driving down the road with six passengers , a picknic basket , a nine meter caravan and one flat tyre and comming to a steep incline ( hill / mountain ) a car with a lot of torque will be able to climb the incline without changing down a gear ( it may get hot ) in comparison a car producing its torque / horse power at high revs will have to chance down to maintain the rpm ( torque ) sorry its not cristal clear . try googling hosrepower / torque graphs and see the results .