Ah, so you buy a Disney (or any division) disc, you sign up to Disney Insiders (as it’s now called) and you enter the code included on the slip of any DVD, Blu-ray or 4K-UHD.
A DVD will net you 100 points, I believe, a BD 150 and a 4K 200. You can also build up points by seeing Disney films in cinemas, etc…it's all explained on the site.
Build up your points and then redeem them *for free!* for additional discs, gifts, books, posters, toys, etc. It's essentially a loyalty scheme, and pretty cool at that. They’re not "special" items that you can't buy anywhere else, though (that's Disney Movie Club, a different thing, but they don't have any special features).
Basically they ask for 100 points per dollar (ish), so a $20 disc would be around 2000 points, etc, though the are essentially discounted, so you wouldn’t be ponying up 3500 points for a $35 disc. They’re usually around 1000 points, some a little more and some less, but roughly equivalent to a dollar per 100.
If you buy a lot of Disney titles, it works out to a nice bunch of "freebies" once in a while, a nice way to catch up on some older titles. Used to be a time when you could trade points for exclusive Movie Club titles, but that was a long time ago.
Hope that helps. It’s all pretty simple and on their site.
