First, just to make sure that everyone knows, a normal pore looks like this.
As mentioned in the previous post, when excess oil is producing, things usually go wrong on your skin. It is because when oil is being produced at a normal rate, it keeps your skin protected, smooth, and hydrated. On the contrary, the excess oil could clog the pore. To make matters worse, dead skin cells on the surface cause even more blockage. From there, depending on what else happens inside the pore, you can have different acne type, a blackhead, whitehead, pimple, cyst, papule, or pustule.