Old iTunes library to new iTunes library - will I loose everything or just music?

I recently got a new phone and new laptop. My old phone was backed up to my old iTunes library but I backed it up to my new iTunes on my new laptop (Tanyel's iPhone). I then set my new phone up from the back up (Tanyel's iPhone) on my new iTunes/laptop. I then wanted to sync the new playlists on my new iTunes/laptop to my new phone but a message said since Tanyel's iPhone was already synced to another iTunes library (old laptop) I would need erase the old library and sync the new one. Would this mean I loose all my apps, contacts etc from my phone or just my music?