Mixture of inorganic compounds, widely used as a white pigment powder / From Wiki

It's also added directly to food; mainly for coloring, but also as a thickener and to keep some powdered food, like confectioner's sugar, from clumping.   

A 2012 study published in the journal Environmental Science & Technology noted that children are especially exposed to titanium dioxide because of the food that contains the food additive and is particularly marketed to children, including candy and cakes.

That being said, titanium dioxide is particularly popular in concealers. ​​As one of the most naturally opaque and pearly-white materials on earth, titanium dioxide has the ability to provide excellent coverage while brightening the skin, whether you’re dealing with blemishes, dark spots, acne, or dark circles under the eye.