Towards is 'in the direction of'. An important difference would be when you are giving directions - if you said 'Go towards the hill, then turn south when you get to the river', that would mean that you go in the direction of the hill, but you don't actually go as far as the hill. You turn before you get there. If you said 'go to the hill, then turn south', the person would go to the actual hill, then start looking for the turn.