If you prefer not to sync your iPhone, iPad, or iPod touch, you don't have to. Depending on the version of macOS your Mac has, you might need to use Finder or iTunes to sync your iPhone, iPad, or iPod touch with your computer. If you have a PC, you'll need to use iTunes to sync it with your iPhone, iPad, or iPod touch. Synchronization usually copies iTunes data from the computer to the iPhone.
The data can include music, movies, photos, and television programs. Syncing is a great way to back up your iPhone. While Apple recommends using iCloud, it's not the only way to sync songs, playlists, albums, movies, TV shows, audiobooks, books, and podcasts. Learn how to sync your iPhone with a Mac with macOS Catalina or later, and with any computer with iTunes.
If you're using a PC or macOS Mojave or an earlier version, the synchronization process is done through iTunes. Synchronizing with the Finder or iTunes keeps compatible content between iPhone and computer up to date. If you have music on your iPhone that doesn't exist in the iTunes library of the computer you're syncing with, that music will be deleted from the iPhone.