who the heck are they?

SNSD is a girl group member consist of 9 members, Taeyeon, Jessica, Sunny, Tiffany, Hyoyeon, Sooyoung, Yuri, Yoona, and Seohyun. They debuted back in 2007 under the entertainment SM Entertainment. The leader of the group is Kim Taeyeon and the youngest member is Seo Juhyun aka Seohyun (her stage name). Want any more information about them? Search up their names on wikipedia. :) 

EXO is a 12 member boy group that consist of Suho, Kai, Sehun, Chanyeol, Baekhyun, Kyungsoo, Kris, Tao, Lay, Luhan, Xiumin, and Chen. EXO debuted in April 2012 and split into two groups, EXO-K and EXO-M. EXO-K promotes in Korea and sings in Korean where as EXO-M sings in Mandrin and promotes in China. Both groups sings the same song but in different language and promotes in two different countries at the same time, making them the most unique group out there.