A painter's paint...basically it lifts tints and you are unlikely to use it outside of mixing colours. When you add white to a colour, creating a tint, the downside is the bleaching of the colour, it can look washed out and at the extreme end can appear chalky (particularly with Titanium white less so with Lead white, and Zinc white).
Usually the idea of adding white is to lighten a colour, but as white is cool in nature it also cools the mix, by adding yellow it lightens while maintaining warmth, I have tried painting without white several times and it is surprising how far you can go with it, it certainly gives a glow to portrait painting, and I suspect some of the old master portraits glow because of a limited use of white.
It is luminous and semi-transparent in nature, the addition of Cadmium Yellow raising the opacity. Now this is a paint you could mix yourself however to accurately measure the 'crumb' of cadmium yellow needed every time is very difficult, with this you are buying consistency.
Pigment - PW4 / PY35, Zinc Oxide / Cadmium Zinc Sulphide
Vehicle - Safflower Oil, Consistency - Buttery