I need understanding a sentence in the express routes

MDN Learn
#1

i need help understand this sentence from the Express tutorial Part 4

Note: The URL /book/create will be matched by a route like /book/:bookId (which will extract a "bookId" value of 'create'). The first route that matches an incoming URL will be used, so if you want to process /book/create URLs separately, their route handler must be defined before your /book/:bookId route.

is the first sentence trying to say that the server will respond with a single book when i request to create a book. is my interpretation wrong

#2

Welcome back, @Nebula!

It will at least try to respond with a single book. I don’t know the actual code, but probably there will be an error because the code of the /book/:bookId page expects a number in the bookId parameter and gets a string (“create”).

Does that make it clearer?

Michael