Purpose of the ingredient, cream of tartar?

I made snickerdoodles for the first time last month. They came out wonderfully btw. This is the only cookie I made that called for cream of tartar.Purpose of the ingredient, cream of tartar?
its an acid powder Combined with baking SODA it makes baking POWDER.





Cream of tartar is also used to give a creamier texture to sugary things like candy and frosting and to stabilize and increase the volume of beaten egg whites.





Cream of tartar can be used to clean brass and copper cookware.Purpose of the ingredient, cream of tartar?
I may be wrong, but I think I remember something about it helping thicken the recipe.
It sort of keeps ur stuff light and crisp. Like in puff pastry and pavlova
Improve the stability of eggs when beating them.