React: What are useDeferredValue() and useTransition()?

1const [isPending, startTransition] = useTransition();
2
3function SearchResults({ query }) {
4  const [results, setResults] = useState([]);
5  
6  function handleChange(e) {
7    // Priority: instantly update input
8    setInputValue(e.target.value);
9    
10    // Low priority: update list (can wait)
11    startTransition(() => {
12      setResults(filterResults(e.target.value));
13    });
14  }
15}

1function Search({ query }) {
2  const deferredQuery = useDeferredValue(query);
3  // deferredQuery updates AFTER query updates
4  return <Results query={deferredQuery} />;
5}