Spotify is finally making a long-awaited feature a reality - the option to download songs to your Apple Watch and stream directly to your headset. Up until now, the watchOS Spotify app was merely a remote control of the iOS app on the iPhone but with the new update, you will be able to stream music offline without the need of a phone at all. Let's say you go out for a run and you don't want to bring your phone with you. Just download your favorite playlists/songs to your watch and then stream them via Bluetooth. That's a highly-requested feature that has been around for a while on...
Source: https://www.gsmarena.com/spotify_now_lets_you_download_songs_to_your_apple_watch-news-49252.php