Those with oily skin know how it feels to have a shine on their face. During adolescence, it is the hormonal imbalance that results in having oily skin. Over exfoliation too, often causes layers of the skin to be formed that gives it the texture. As the light reflects off the skin easily, the skin appears shiny.
Also, the hyper-active sebaceous glands cause more oil secretion that gives your skin a shiny appearance. The skin appears greasy and attracts dirt and dust easily giving you an unkempt and dull look.
Applying makeup on top of oily skin does not hide the shine or the surface oil. After some time, your face starts appearing black and in places becomes patchy making certain areas of the face appear uneven.