The Man of Steel and the Dark Knight. They're two of the most well-known, popular, and instantly recognizable super heroes in all of fiction. They both strive to uphold justice. They both take on dangerous criminals and super-powered madmen. They both serve on the legendary Justice League. Separately, they're two of the world's greatest super heroes. Together, they're the World's Finest.
The Justice League is known for many things: uniting the World's Greatest Super Heroes under the banner of battling evil and upholding truth and justice; multiple incarnations throughout the various years featuring heroes from all across the DC Universe; even amazing animated programs and original animated films worthy of re-watch after re-watch even though you can quote every line by heart.
However, one of the best things the JL is known for: awe-inspiring fights and kick ass throwdowns against some of the biggest and baddest villains in the DC Universe.