You might have noticed some additional questions popping up on your iPhone and iPad lately. It is hard to determine what to do and how to undo if you make the "wrong choice" at any given moment.
Apple's Overview on Privacy is a good place to start. The App Tracking Transparency section has both a PDF and a video to help get you started. Other pages include Features, Control, Labels, Transparency Report and Privacy Policy.
Like many unfamiliar articles, you will want to read this site through. After you have experienced some of the improved privacy features then return and read this site again. Ah ha! You will make new connections between the details and personal experience. Share the site with your friends and family. Then read it again, and again.
Another Apple publication is a good read: Device and Data Access when Personal Safety is At Risk is worth reading several times. The table of contents includes: Protect your device, Protect your Apple ID, Check privacy settings, Shared Albums in Photos Delete unknown third-party apps, Phishing and fraudulent requests to share info, Checklist - If you want to see if anyone else has access to your device accounts, Checklist - If you want to make sure no one else can see your location ... and more. You can save this PDF to Apple Books for easy offline reading.