When you connect Apple Music to Alexo, you will be able to set Apple's streaming service as the default music source so that Alexa will play songs from it by default. Alexa will have access to your personal library and playlists that you create and listen to playback controls during playback. The voice assistant will not be able to add songs to your library or play music you've added manually from your music collection.
Support on Echo devices is indicated only by a second voice-controlled speaker that works directly with Apple Music, except for ApplePodPod itself. It is unclear whether other speakers with Alex, such as Sonos One, will offer similar compatibility, although the announcement in the Amazon blog is audibly restricted to Echo speakers only.