I don't get the "Plot" in "Old Possums Book on Practical Cats"?

Old Possum's Book of Practical Cats covers thirteen distinct characters and plot lines. Each character has his or her poem and is thoroughly discussed. There are also two poems dedicated to the naming and addressing of cats; these chapters do not introduce any characters, but serve as an opening and a closing to the work, thoroughly acquainting the reader with the behavior of cats. The cats range from very practical to highly impractical.