Route handlers (the callbacks for `app.get()`, `app.post()`, etc.) are just middleware that does not call `next()`. If a middleware function doesn’t call `next()`, then Express will never call the subsequent middleware, which can be the right choice if that middleware function sends an HTTP response.
Routers, like `express.Router()`, are also middleware functions. They just happen to be middleware functions that have their own middleware stack.
Want to learn more? Get the tutorial and become an Express expert today!