What is the conflict of a story?

It is the happy ending of a story.

It is the bad character in a story.

It is the problem that characters face.

The conflict of a story refers to the problem or struggle that the characters face. It is what drives the plot forward and creates tension or obstacles for the characters to overcome. The conflict can be internal (within a character's mind or emotions) or external (between characters or with the outside world). It is not necessarily associated with the ending of a story or the presence of a bad character.