GDPR: Here's what I do with your data
AddThis: See those social media icons on the left-hand side of your screen of every page of this blog? I use a plugin for that called AddThis. The only data I get from that is analytics-related: how many people shared the posts, which social media platforms have been used most frequently to share pages of my blog/website, and how many people have accessed my website pages. I receive no personally-identifying information from this. I use this data only to get an idea of how popular my pages are.
Google Analytics: Our dear friends at Google give me data about a whole myriad of things: how many people visited my site, whether they were repeat or unique visitors, the source of these visitors, how much time they spent on each page, the language of their computers/browsers, their locations, the operating systems and browsers they're using, whether they are on mobile or desktop, demographic data, and much, much more. I get basically the same information from Squarspace analytics, though it's much less comprehensive than that of Google (note: I use Squarespace to host this website).
Honestly, I only look at how many people visited my website over a given time period. I don't care about or use any of the other stuff. I just don't have the time or interest to do so.
Newsletter: If you sign up to my newsletter (which you should right here!) I obviously get your email address. What do I do with this? Send you newsletters with updates about the latest blog posts. That's it.