Best answer by MrKeith
It is importing the music from the folder locations you have specified (and can change) in your set up.
If you have also told it to import from the location where your iTunes library file is located, it will import your iTunes playlists as Imported Playlists.
You don't manage or delete music within Sonos. You maintain the music in its folders (possibly through iTunes). Sonos is updated every time you sync the Sonos library.