A concealer or color corrector is a type of cosmetic that is used to mask dark circles, age spots, large pores, and other small blemishes visible on the skin. It is similar to foundation, but thicker and used to hide different pigments by blending the imperfection into the surrounding skin tone. A corrector is usually a specific shade/color that will cancel out the shade/color of what you put it on top of. For example, a green corrector cancels redness of zits/rosacea, a peach corrector cancels purple tinges under the eye