I think this ended up on the front page because people instinctively upvoted Zed-something.

It started with Go, then Rust, then Zed. Whatever happened to giving a unique name like Hadoop?

You can activate an OpenType feature to change the shape of the l to be more visually distinct from the uppercase I

They are made for shorter texts that are often written in a bigger font. Again I talk about this in a very general way because it depends on the font and other factors. But usually this includes things like headings. So they would use slightly different proportions that wouldn't work that well at small sizes, but stand out more in bigger sizes compared to the "text" variant.

So in this case you would use Zed Text for all your larger text blocks and Zed Display for headings or maybe emphasized words. But to be honest, since they are pretty close visually, you can get away with using Zed Text for everything imho.

Text versions are used for longer text, and are usually optimised for smaller type sizes and readability.