What is climax in a story?

The turning point, when the story changes

It means the key moments, within the book, movie etc. The most effective or what the story is really made for.

The climax is the height of the action and also the turning point in a story, imagine a pyramid, climbing up would be the rising action, the top of the pyramid would be the climax, then you would have to go down and that's the turning point and the falling action,

The part you's want to read most! the most exciting part! the part you took the story to read for!
A climax is the most interesting/thrilling part of the story.it is the emotional high point of the story.
The climax of a story is the thing that makes you curious and leads you to the conflict of the story
The climax of the story is the turning point of the story; the moment when the ultimate suspence reaches its peak.

climax is the problem of the story.

Many believe the climax is the most intense or interesting part of the movie. This is a common mistake as the climax is when the theme is proven, which commonly is the most interesting or memorable scene. After the climax, the story cannot be proven anymore, or there is no more story to tell other than the conclusion. [Example Lord of The Rings - when the hobbit finally destroys the ring is the climax. The theme is, "Even the smallest person in the world can make the biggest difference."
It is the most interesting part in a book