What's the difference between a Watch and an informer?

What’s the difference between:

        const watch = new k8s.Watch(kubeConfig);
        watch.watch(
            '/api/v1/namespaces/default/pods',
            {},
            (type, obj) => {
                switch (type) {
                    case 'ADDED':  console.log('added'); break;
                    case 'MODIFIED': console.log('modified'); break;
                    case 'DELETED': console.log('deleted'); break;
                }
            },
            err => {
                console.log('error');
            }
        );

and:

const listFn = () => k8sApi.listPodForAllNamespaces();

const informer = k8s.makeInformer(kc, '/api/v1/namespaces/default/pods', listFn);

informer.on('add', (obj: k8s.V1Pod) => { console.log(`Added: ${obj.metadata!.name}`); });
informer.on('update', (obj: k8s.V1Pod) => { console.log(`Updated: ${obj.metadata!.name}`); });
informer.on('delete', (obj: k8s.V1Pod) => { console.log(`Deleted: ${obj.metadata!.name}`); });

informer.start();

It seems like the informer is doing a lot more stuff. There’s a whole in-memory cache of all the Kubernetes objects being watched?

And why is there a listFn and a path in the informer case? In this example (which was taken from the official example, the list function is getting pods for all namespaces whereas the endpoint is only fetching pods in the default namespace, which seems wrong.