Milf-has had at least one *****, and although she is in the range of 30-45 years old, has maintained her looks and body...because the fact is, the stress of raising a *****, will wear you down just as much, if not more then giving birth.
Any 18-25 year old can have a ***, and bounce back if she works at it, but to hold it together for another 10 years...that's the milf badge right there.
Mature-is in the gilf category, but could also be childless, but she should be over 50...more like 55.
Cougars-those can be milf's or mature...main thing here is, they should fall between 35 to 55 and have been in a previous long term relationship, that has left them sufficiently unsatisfied, or disillusioned enough to say fuck what everyone else thinks, I'm getting mine, and they ACTIVELY pursue meaningless sexual liaisons with younger men...aged from 18 to about 25.