Someone please clarify this for me, it says that Facebook will track you across "Websites and apps". I get that they will know what I am doing in their app but will they be able to see what is in my email, my Safari browsing, my Apple TV, YouTube watch history, SMS?!

All the Ways Facebook Tracks You—and How to Limit It
If you have a Facebook account—and even if you don't—the company is going to collect data about you. But you can at least control how it gets used.
Site owners are able to build a profile of the people who visit them, which is in turn shared with Facebook to build an even more extensive profile of their users. And don't forget that Facebook owns a slew of apps as well, most notably WhatsApp.
And I am sure the article is only scratching the surface of what Facebook is doing here.