MILF
MILF is the common term for a sexy older woman, usually a mother. A cougar is normally an older woman who likes younger guys and is often a lot more direct about what she wants. Puma sometimes means a younger cougar, but nobody really cares about any exact age rule.
Mature lady is the general term used on casual dating, escort and porn sites for older women, usually 40+. If you spend enough time dating older women, the labels all start to overlap anyway. MILF escorts are extremely popular on escort sites in North America, while in Europe the word used is usually "Cougar escorts" and in India its Aunty escorts.
