Nightcore is a musical genre. It is composed of sped-up versions of songs.
How to create Nightcore
To create a Nightcore song, open up Audacity. Open your favorite song, and speed it up with an increment of 75.000. Save it, and open up the video editor of your choice. Find a picture of an anime girl, and stretch it to the length of your song on the timeline. Export the video, and publish it to YouTube. You're done, now ~SHUT UP AND ENJOY THE NIGHTCORE~