Semen or sperm is a fluid that contains spermatozoa. It is
secreted by the gonads (sexual glands) of male or hermaphroditic
animals and humans for fertilization of female ova. A definite
portion of semen discharged by an animal or human is known as
ejaculate, and the process of discharge is called ejaculation. Like
blood, semen consists of two parts, the cellular part (spermatozoa)
and noncellular part (seminal plasma). It contains the
spermatozoa.
Depending on the species of animals, spermatozoa can fertilize ova
externally or internally. In external fertilization, the
spermatozoa fertilize the ova outside the female organisms which
expelled the ova. Female fish, for example, spawn ova into their
aquatic environment. Those ova meet with spermatozoa which have
been carried away inside semen secreted by male fish.
By internal fertilization, on the other hand, ova get fertilized
inside a female organism. Internal fertilization takes places after
insemination of a female by a male through copulation. In low
vertebrates (amphibians, reptiles or birds and monotreme mammals),
copulation is cloacal. In marsupial mammals and placental mammals,
copulation is vaginal.
Mammalian semen is a whitish, milky fluid, very viscous, containing
water and small amounts of salt, protein, and fructose. It varies
from being without scent and taste, to having a strong taste and
smell of ammonia. Many people claim that one's diet can
alter the taste of semen for better or worse, but this has not been
scientifically proven.
doesn't help much, just some bg
info on semen from a site. 
