The End is a barren, empty dimensional plane containing a large floating island of a unique material called End Stone, dotted with Obsidian pillars. This dimension is populated by a vast number of Endermen and their Ender Dragon leader. Once one enters the End, there is no way out without dying, except to defeat the Ender Dragon, although doing so will destroy The End.
The End was destroyed when Alban Pahlke and Aria Shadewood destroyed the Ender Dragon, and only barely escaped with their lives.