What is the difference between /books and /books/{id}?

/books is usually an endpoint for working with a collection of books. For example, GET /books returns a list of all books, POST /books creates a new book.

/books/{id} is an endpoint for working with a specific book by its unique identifier. For example, GET /books/123 returns information about the book with ID 123, PUT /books/123 updates it, DELETE /books/123 deletes it.

Thus, /books operates on a set of resources, and /books/{id} on a single specific resource.