Suppose that the results of this segment show that 37% of users are on desktop. This info would be incredibly useful if you’re running mobile ads exclusively; perhaps you didn’t realize that as much as 37% of your audience across channels is on desktop. Or if you have a site that works best on desktop, the fact that 63% of your users aren’t on desktop could push you to get more mobile-friendly.

If you're the type of person who doesn't really use Facebook for anything you wouldn't normally consider public anyway, you should take note: everything you do on the web is fair game. If what Cubrilovic and Winer are saying is true, Facebook considers visiting a web site or service that's connected to Facebook the same thing as broadcasting it to your friends at worst, and permission for them to know you're there at best. Facebook Video I Made Discussing Quotes From Dr. Peterson and Dr. Duchesne

At this point, the SDK is set up, and your application can pass app install events to Facebook for measurement and tracking purposes. With this data, you can track and measure app installs and also optimize your ads delivery for mobile app installs. Now that you've implemented the SDK for your platform, you should also add code for additional app events you want to track and measure, such as purchases.

You can use the Facebook pixel to track your website visitors' actions. This is called conversion tracking. Tracked conversions appear in the Facebook Ads Manager and the Facebook Analytics dashboard, where they can be used to analyze the effectiveness of your conversion funnel and to calculate your return on ad investment. You can also use tracked conversions to define custom audiences for ad optimization and dynamic ad campaigns. Once you have defined custom audiences, we can use them to identify other Facebook users who are likely to convert and target them with your ads. How to prepare and market using Facebook Ads