Vladimir Propp was a clever man who studied stories from a long time ago. He found that lots of stories have things in common, like characters and events that happen. He called these things "functions."
Some of the characters he found were heroes, villains, and helpers. The heroes are usually the main character and do good things. The villains are bad guys who make the hero's life hard. Helpers are people or animals who help the hero.
Propp also found that lots of stories have similar events that happen. For example, almost every story has a problem that needs to be solved. Sometimes, the hero needs to go on a journey to find something, like a treasure or a person. And in most stories, there is a big fight or battle at the end.
Propp's ideas about these characters and events have helped people understand how stories work. People can use his ideas to write their own stories or to help them understand stories they read.