what all does the service do

You can search this site using the word [Privacy] Example results: https://support.mozilla.org/en-US/kb/recommended-firefox-privacy-and-security-settings-families https://support.mozilla.org/en-US/kb/how-do-i-change-my-privacy-features And of course it depends upon your device and their settings to. There is a dedicated forum for Android devices: https://support.mozilla.org/en-US/questions/mobile