What is plot structure and what do the elements such as exposition, rising action and so on mean?

Plot structure is how the entire story is set up with the parts being the exposition, the rising action, the climax, the falling action, and the resolution.

The exposition is the beginning of the story where the characters, setting, background and the basics are revealed.

The rising action is where the story gets a little more bumpy and the conflict is revealed.

The climax is height of the story. This is where the characters face the issue of the story

The falling action is what happens right after the climax. This is the effect that facing the issue has had on the story. It begins to wrap up the story.

The resolution is the ending of the story. Whether it is a cliffhanger or closes all the lose ends, it end with a resolution.