Whether you use the technical term fellatio or call it a blowjob, going down, giving head, or something else, performing fellatio is an act that requires a lot of trust and a little bit of knowledge. If you believe everything you hear, you might think that guys love this so much technique and intent don't matter. Think again. In reality, there is a lot of variation in fellatio skills, and knowing how to read your partner, what to do to him, and when to do it can make all the difference. We mostly think of fellatio as being one person licking or sucking a partner's penis. Keep in mind that while most men have penises, not all do.
During puberty, your testicles testes change and begin to produce the male hormone testosterone and sperm. Sperm are so tiny that they can only be seen under a microscope. Testicles need to stay cool for sperm to develop normally. This is why they hang outside the body in a sac bag called the scrotum. It is quite normal for one testicle to be larger or to hang lower than the other. One of the most common cancers for men between the ages of 15 and 30 years is cancer of the testes.
Fellatio also known as fellation ,  and in slang as blowjob , BJ , giving head , or sucking off  is an oral sex act involving the use of the mouth including the lips and tongue or throat performed by a person on the penis of another person. Fellatio can be sexually arousing for both participants, and may lead to orgasm for the partner being fellated. Most countries do not have laws banning the practice of oral sex, though some cultures may consider it taboo.
Penis-in-vagina sex is not the be-all-end-all of sex. Oral sex can be just as pleasurable — if not more so — than penetrative sex. You know whose genital juice tastes like cookies and cream? We all have a taste down there. Avoid garlic, onions, asparagus, and cabbage, which reportedly make for a less-than-pleasant flavor.