As if to thank ファン for her win at the '2014 MAMA', IU(アイユー) 投稿されました on her Twitter, "I'm happy. It's all thanks to you. This is a present." She then provided the link to the audio heard above, which avid ファン of the singer may recognize it to be the full version of the 前 snippet she let ファン hear on a ファン community page.
IU, of course, wrote and composed the song herself, so make sure to give it a listen above!
(link)