iTunes will periodically send details about your song library to Apple servers. This feature is enabled by default and may be perceived as invasive by some users. Here are the instructions on how to opt out of this feature in iTunes.

How To Prevent iTunes from Sharing Information About Your Library

Open iTunes and sign in with your Apple ID. Click on Edit > Preferences > Store tab. Clear the Share details about your library with Apple checkbox and click on OK:

N.B. In doing so, you'll also disable the program's ability to automatically fetch missing album artwork.