The thing that stands out the most is the graphic retouching that the game has undergone. The black and white of the original game has given way to a much more careful esthetic with graphics that have some elements (like Link himself) that are far superior to those you see in the Super Nintendo games.
Leaving the graphics aside, in terms of the story and gameplay, Legend Of Zelda: Link's Awakening is almost identical to the original game. You will begin Link's adventure by shipwrecking on an unknown island and being rescued by a girl, and you will continue going along the beach to recover your sword. From there, everything will play out as usual: the action, dungeons, adventures, etc.
Legend Of Zelda: Link's Awakening is an excellent game that allows players on a PC to experience one of the best games for Nintendo's first portable device, with tons of improvements on the original game.