Generator functions allow us to describe sequences using imperative code.

Generator functions contain at least one use of the yield keyword.

Generators are iterators. When the iterator is advanced with next() the generator starts or resumes execution up to and including the next yield.

Each call to a generator function creates a new generator object.

Generators can maintain explicit state in local variables between iterations.

Generators are lazy and so can model infinite series of data.

Generator expressions have a similar syntactic form to list comprehensions and allow for a more declarative and concise way of creating generator objects.