Fertilization is the process of union of sperm and an egg. It results in formation of a zygote.
Sperms which are ejaculated from the male during intercourse will swim up towards the oocyte which is called as egg cell in uterine tubes. It passes its way through the vagina and uterus and when egg cell is released into the fallopian tube then fertilization will take place.
The sperm and the egg are known as gametes and thus each of them contains half of the genetic information that is important for reproduction. When sperm cell fertilizes an egg cell then genetic information united. It means 23 chromosomes from the sperm cell combines with 23 chromosomes of the egg cell that results in formation of 46-chromosome cell which is known as zygote. The zygote travels toward the uterus and divides to become a blastocyst.