What is the useFetcher hook in Remix?

The useFetcher hook in Remix allows performing form submissions and loader data fetches without navigating. It is used for background mutations and non-navigation interactions. Unlike the main navigation, fetchers don't change the URL. Common uses: Like buttons: submit a like without navigating. Inline forms: edit a field in place. Data loading: load additional data on scroll or user interaction. Usage: const fetcher = useFetcher(); return <fetcher.Form method="post" action="/like"><button>Like</button></fetcher.Form>;. Check state: fetcher.state — "idle" | "loading" | "submitting". Access returned data: fetcher.data. Load data without form: fetcher.load("/api/suggestions?q=search"). Multiple fetchers can run simultaneously. The key distinction: useNavigation reflects the main navigation state; useFetcher is for background operations that don't change the URL.