Starting on the male side, sperm (male sex cells) are produced in the semineferous tubules of the testes. The sperm are stored in the vas deferens, a storage tube located on top of each testacle. In the process of sexual intercourse, the sperm are mixed with semen, a fluid designed to keep the sperm alive as they journey through the urethra, a tube traveling through the penis.
On the female side, an egg is ejected through the ovary wall, and starts it's journey down the fallopian tube on it's way to the uterus. In the process of intercourse, sperm are introduced into the female vagina, which then travel into the uterus. The sperm continue to travel upwards into the fallopian tubes, where one sperm fertilizes the egg. The fertilized egg, now called a zygote, continues to travel down the fallopian tube to the uterus, where it will implant into the the uterine wall. The zygote, now about a week old, has undergone multiple cell divisions and is now called an embryo. The embryo establishes an umbilical cord, a connection between the developing embryo and the mother's blood supply.
After about 8 weeks, the embryo has continued to undergo cell divisions, most major organ systems are developed or are in the process of developing. The embryo is now called a fetus, and will continue to be developed and nourished by the mother until about the 40th week, where the child will be born.