The post lists as much iterator variants as possible: how they are constructed and what are they signatures.

Why? We want to do more with iterators:

• async iteration
• adress-sensitive (self-referential) iterators
• iterators that can lend items with a lifetime
• conditionnally terminate early
• take external arguments on each call to .next()

and also because "I've started hearing talk about potentially (soft-)deprecating Iterator." and the author worked on the Node.js Streams WG through the mid-2010s.