Pinboard has been a staple of the nerdy community for years, so you probably already know all this, but I have to mention this every now and again.
Pinboard is a service for saving links for later. Think of it like a Pocket or Instapaper-like service, but without the custom reading interface. It's not a read-later service, it's for saving certain sites for access later. I think of it kind of like my own personal Google. I can go to the Pinboard site and search for something very specific and get only pages I've looked at before, not all the noise you typically get in a Google result.
Pinboard also has a web page archiving feature you can pay extra for, which will save the HTML content of the sites you save so that you can access them forever. This is helpful if you want to save a page that may be taken down by the author for some reason, or the permalink changes so the link you saved no longer works. There's the added benefit as well that this adds the full content of each article to your search results in Pinboard, so it's even easier to find things later.
You can use Pinboard however you would like, but I use it as a sort of read later service, even though it's not technically built for that. I add a few links per day to my account and they get saved to my "unread" list. I don't really save long form content here, but more things that I want to consume on the author's website, not in Instapaper's stripped down environment.
Out of curiosity, I used Pinboard's API to pull my entire list of bookmarks since I started using it in 2010, and it turns out I have saved 15,471 URLs to the service since then. Because I'm a sucker for data visualizations, I also broke down how many pieces I add to my archive per day every year since I joined.