Syncing iphone to new itunes

I changed my hard disk and thus had to reinstall itunes, when manually syncing my music I got the following message:

The iphone xxxxx is synced with another itunes library, do you want to erase this iphone and sync with this itunes library?

An iphone can only be synced with only one itunes library at a time. Erasing and syncing replaces the contents of this iphone with the contents of this itunes library.

What does that mean? Will it only erase my videos and music? or will it