Syncing iPod with this iTunes Library will replace media from another iTunes Library on this Mac

Hello. I had an issue with one of my IPod's where I must have disconnected too soon or something so that it is no longer recognized by my iTunes Library. I was about to re-sync all of the playlists that are currently on it but when I got the above message I became concerned that it might remove songs from my Mac. In the past I have seen media disappear from my Mac so I must ask, Is this even possible? In addition, does this message have something to do with iTunes syncing from multiple libraries?