Silicone is derived from a natural product called Silica but following a chemical process it becomes a synthetic ingredient that is safe for cosmetic use. There are many different types of Silicone, each slightly modified to provide varying benefits; from protecting your hair from damage to locking moisture into the skin and making mascara waterproof. They are added in small quantities to skin care products in order to make heavy creams feel lighter on the skin while also adding a luxurious texture to more basic formulations.
They are also great for making beauty products long-lasting, with face primers being the most common to use Silicones. They leave a velvety smooth film over the skin, without clogging the pores, so they are great in shine controlling products designed for acne prone and oily skins.