n. Refers to a very specific type of male gay love. One male is distinctively older, say 40+. The other male is younger, but past puberty (16-24). As opposed to pedophilia, both parties are sexually mature-- and the younger man is willing. Please note in the US, sex with anyone under 18 in illegal-- so pederasty lies on a thin line legally. Pedophilia, on the otherhand, is sex with a pre-pubescent child of either gender.
Pederasty, as a general rule, has stayed as a structure among gays because it has many distinct benefits. For the younger man, it is an opportunity to learn from someone with more experience-- with sex and the world; it is also a way of helping the younger man as he is in a state of self-discovery. For the older man, it is first of all a chance to have sex with a twink, but moreover a chance to pass down wisdom and experience. In a life-style where you have no children, it is a chance to exercise paternal instincts.
Note: the older man is called a Pederast.
In areas of Greece where Zeus and Apollo were worshipped, it's thought that the older men who groomed the younger soldiers engaged in some degree of pederasty.
Although confused with any form of sex between a prepubescent / adolescent and an adult, pederasty refers to the practice of a sexual relationship between a pubescent / adolescent boy and an adult male. The practice has faced wide moral condemnation (against the older male - the pederast) in the 20th and 21st centuries, especially since the 1990s.
Just like sex in general, the term does not hold any power in determining the consensuality of the relationship, indeed it is used by the media to describe the statistically rare cases in which the younger 'partner' is being coerced (in which case, the Pederast is unlikely to hold the physical and emotional beauty of the boy in high regard).
A Pederast or their lover will often refer to the relationship as having a mentoring function, in which the younger partner is taught the joys of sex alongside more general pedagogic functions.
Society widely characterises the man as the dominant partner (he tends to be the one who seeks the relationship), but modern pederastic relationships tend to show a 50:50 balance, regarding who starts individual sex acts. Studies by Gerbener and Sandfort quite surprisingly show that it is the boy who penetrates the man in most cases (although penetration is extremely rare, so neither study is statistically significant alone). These findings probably represent the physical and emotional considerations of the couple - it makes sense that 1 goes into 2, not the other way around, plus the benefit ...