Docs lack a good summary page comparing three concepts. The main question is how do I tell if something is a sequence, generator, iterator or iterable? I found myself puzzled that range() is neither generator or iterator.

Briefly,
An iterable is an object that can be iterated with an iterator.
An iterator is an iterable that responds to next() calls, including the implicit calls in a for statement.
A generator is an iterator created by a generator function, which is a function with a yield keyword in its body.
A sequence is an iterable with minimal sequence methods.

The four terms are all in the glossary. The entry for iterable already points to the other three. What do you think is missing?

A range (as documented) is an immutable sequence.

To make the subset relationships clear in the iterable entry, perhaps replace
  See also iterator, sequence, and generator. 
with
  Some iterables are iterators and some iterators are generators. Some iterables are sequences. For details, see iterator, sequence, and generator.

I see that 'generator' is currently used in the 3.3.1 glossary for 'generator function' and there is no entry for generator (object) proper. I thought that had been fixed after pydev discussion.