During puberty, a boy's skin on his face, neck, back and chest will eventually begin to overproduce a type of oil called sebum. Sebum is normally a good substance -- it keeps the skin waterproof and fends off harmful bacteria. But too much is definitely not a good thing. Along with excess oil, the pubescent skin is also sloughing off skin cells at a higher rate, and these skin cells -- and the extra oils -- are trying to exit the body by traveling through hair follicles and pores to the surface of the skin. When these pores and follicles get clogged up with this excess matter, there is a pileup as the skin and oil behind the blockage start building up without anywhere to escape. A form of bacteria known as Propionibacterium acnes (P. acnes for short) gets in the mix and causes the blockage to become inflamed. This pushes it outward, creating the visual sensation known as a "zit."
There are many forms of acne, but the most common one is acne vulgaris. Acne vulgaris is responsible for your garden-variety pimples, blackheads, whiteheads and the cyst-looking large bumps. There's pretty much no escaping acne vulgaris -- it afflicts practically everyone at some point, and boys get it worse than girls during puberty. (After puberty, it's a different story: Women have much more trouble with adult acne than men.)
If you're a pubescent boy dealing with acne, this is your best bet: Wash your face gently twice a day, shower immediately after working up a sweat and don't pick at your face. Don't go overboard trying to clean your face, either, because excessive scrubbing and agitating the skin can make everything worse.
Products containing benzoyl peroxide or salicylic acid can help prevent or control acne by drying out the skin, killing bacteria and helping the follicles clear themselves of dead skin cells.
Don't get too stressed out if one thing or another doesn't seem to be helping -- it often takes quite a bit of experimentation before you discover the right cure (or combination of cures). Your doctor or dermatologist will be more than happy to help you in your quest for clear skin (and you can also find out lots more about acne by checking out How Acne Works).
Next, we'll examine a question that has tormented the minds of pubescent girls since the beginning of time: "Why are pubescent boys insane in the brain?"