While we often use plot and story interchangeably, strictly speaking, plot and story in literature are not interchangeable terms. An easy way to remember the difference is that story is internal and plot is external. Going further, story tells us about the characters, their backstories, and their current conflicts. The book’s setting is also part of the story.
Plot consists of actions that take place during the book.
Story
Let’s take Romeo & Juliet, for example. Warning: spoilers ahead.
The protagonists are a teenage girl and a teenage boy. Their relevant backstory is that their families have been feuding for generations. Juliet’s conflict at the beginning of the story is that her family wants her to marry Paris, but she isn’t interested. Romeo’s conflict at the beginning of the story is that he wants to be with Rosaline, but she isn’t interested in him. The setting is 14-century Verona.
That is the story. Secondary but still important parts of the story are the friends and relatives they care for and who care for them. All of the characters have personality traits that are part of the story and drive the plot. For example, the protagonists are passionate and impulsive. Their personalities cause them to react to the plot in certain ways, and their reactions are the story, not the plot.