Original: The libretto for The Seasons was provided to Haydn, just as with The Creation, by Baron Gottfried van Swieten, an Austrian nobleman who had also exercised an important influence on the career of Mozart.
Simplified: The libretto (the words) had been written by Baron Gottfried van Swieten who was an Austrian nobleman who liked music. He had helped Mozart in his career and now he was helping Haydn.