The Adventure of Link brought many things to the series like magic, towns, and more complicated swordplay. Instead of items that you use on a daily basis, you use magic spells which you collect in every town. These magic spells can range from the greatly needed health spell, to the more obscure Fairy spell which turns Link into a fairy so he can fly or go through locked doors. Of course you got items but they only played a role on the overworld and did not hold many purposes other than clear obstacles on the overworld. As for the towns, they played a big role in AoL because you could get your health and magic filled back up and get a new magic spell to aid you. This also gives way to more diverse NPC's that are different than your every day Old man. The last point I will expand on is the complicated swordplay, there were several sword techniques that you could use at the beginning which are the stab and the crouch stab. As your quest got more difficult, you could get two more sword moves, the upward and downward slashes which, when you jump allows you to stab up or down. The combat between enemies is also very complicated with very many sword wielding enemies that have many of the same moves as you. Well that does it for what I know AoL brought to the series.
-Tony Fischer