What is K-pop? It's Korean pop music.
The K-pop genre was born in the 90's, but really took off in the 21st century. K-pop consists of male and female performers, called idols, much like American pop. K-pop however has a significant number of male and female performance groups. Think late 90's groups like Spice Girls, Backstreet Boys, etc.
I really love K-pop because there is a dance in every music video. It is similmar to Bollywood in that way. K-pop fans, including myself, watch music videos and learn the dances. Then when the song comes on we dance along with the idols.
The Internet widened the demographic for K-pop. Now K-pop fans can be found globally, and not just in Southeast Asia.
If you are interested in listening to some K-pop, I suggest going to the Official SM Entertainment website and the official YG Entertainment website.
Below is a dance cover of Hoot by SNSD that my friends and I filmed.