The Falcon's Wings / Falcon Wings are a set of cosmetic wings that can be farmed in Diablo 3, and unlike most other wings, you can get them from a drop. The only other wings that can be dropped in-game are the Cosmic Wings.
To get the Falcon's Wings, you need to find a chest called Mysterious Chest in Gardens of Hope Tier 1. The chest looks exactly like the regular chests that can spawn in that area, and also share spawn points with them. The spawn chance of the chest is somewhat low (somewhere around 1 % for each game loaded), so prepare to spend some time before you get the wings. Most people get their within a few hours, but it can take longer if you are really unlucky.
The general strategy for farming these wings are to teleport to Gardens of Hope Tier 1 and go north until you get to a crossing. Now go left and chest for chests until you reach the end of the level, where Rakanoth is. If you haven't found the chest, exit the game and restart. This means that each run will be really fast, but you will need a lot of runs before you find it.