These take the form /api/books/<id>. These methods are only applicable for an already existing resource. They will update a given resource with the data or new state of the resource provided in the request's body. PUT expects a resource's new state to be provided in completion, including fields that haven't changed. PATCH can be thought of as a more relaxed version of PUT because we do not need to provide the complete new state but only the fields that need to be updated.