So i don't fully understand what the sync toggle button in the notification center of the galaxy s6 does. What does it actually do? And if i turn it off what happens?
Welcome to Android Central! It toggles Auto-Sync for your Google account. So if you go to the Settings>Accounts, select Google and your Google account, any of the checked services will sync automatically when you have Auto-Sync on, and won't if it's toggled off. You can still manually sync most of these services. See this support page: https://support.google.com/nexus/answer/2840875?hl=en