Generator functions in Python : Generator functions in Python are special functions that can be used to create iterable objects. Unlike regular functions that return a single value, generator functions use the yield statement to return a sequence of values one at a time. This allows for efficient memory usage as values are generated on-the-fly, making them suitable for handling large data streams or generating infinite sequences.

Generator expressions in Python : Generator expressions in Python provide a concise way to create generator objects. They are similar to list comprehensions but produce a generator instead of a list. Generator expressions are enclosed in parentheses and can be used in situations where generating a sequence of values on-the-go is more memory-efficient than creating and storing a list.

Yield statement in Python programming language : The yield statement in Python is used within generator functions to produce a value and suspend the function's execution temporarily. Unlike return statements that terminate a function, yield allows the function to retain its state and resume from where it left off when the next value is requested. This enables generator functions to generate a series of values iteratively in a memory-efficient manner.