Iteration is a general term for taking each item of something, one after another. Any time you use a loop, explicit or implicit, to go over a group of items, that is iteration.
iterator have specific meanings.
iterable is an object that has an
__iter__ method which returns an
iterator, or which defines a
__getitem__ method that can take sequential indexes starting from zero (and raises an
IndexError when the indexes are no longer valid). So an
iterable is an object that you can get an
iterator is an object with a
next (Python 2) or
__next__ (Python 3) method.
Whenever you use a
for loop, or
map, or a list comprehension, etc. in Python, the
next method is called automatically to get each item from the
iterator, thus going through the process of iteration.