Is herobrine in minecraft real or is just a story?

Maybe

Herobine just a story. People have torn the code of the game apart and there's nothing in it. Furthermore Notch has torn the 'backstory' of Herobrine down as well, and public records back him on that.

That being said, a lot of trolls use a skin as it is described when they grief people online, and there are several mods that add Herobrine as well.

Notch confirmed thats herobrine is not a real thing just a hoax

Herobrine exists, he is in mods. Look up Popularmmos, he has a huge mod pack a Herobrine mod might be in the mod pack.