About.com defines gametes as haploid cells produced via the special cell division process of meiosis. Nature Education notes that gametes contain half the number of chromosomes as compared to cells in the rest of the body.
The terminology associated with chromosome number uses "haploid" to mean that a cell contains a single complete set of chromosomes, as explained by Princeton.edu's page on ploidy. "Ploidy" refers to the number of chromosomes in an individual cell nucleus, and while haploid cells such as gametes contain one complete set, the cells of the body contain two sets and are called "diploid." Diploid cells contain chromosomes from one set paired with chromosomes from the second set in what is known as a homologous pair.
Each member of a homologous pair represents a chromosome contributed either from the mother or father's gamete. The chromosome sets of the mother and father are combined during the process of fertilization. The large, stationary gamete called an ovum is penetrated by the mobile gamete called a sperm cell, and the nucleus of the sperm combines with the nucleus of the ovum. The fusion of the cell nuclei causes the individual chromosome sets of the cells to combine and produce a unique diploid set. The fused gametes are now a single cell, called a zygote, which divides again and again until it grows into a new animal or plant.