Reproductive cells in animals, called gametes, are examples of haploid cells. Both male and female reproductive cells, known respectively as sperm and egg cells, are haploid in that they each possess one copy of each type of chromosome that, when joined with other haploid cells, forms a single, complete chromosome set.
Haploid gametes are created via the biological process of meiosis, which splits a diploid parent cell into genetically unique daughter cells. Unlike haploid cells, diploid cells possess two copies of each chromosome, forming two chromosomal sets. Once the haploid daughter cells are created through meiosis, they can combine with an opposite-sex gamete to form a diploid zygote that develops into a new organism. This method of generating new offspring through the fusion of two cells, each containing half the total number of chromosomes an organism of that species normally possesses, is called sexual reproduction.
Body cells are diploid in animals. Whereas gametes are produced through meiosis, diploid body cells are created through a different method of cell replication called mitosis. This process creates daughter cells that are exact genetic copies. The goal of this process is not to make gametes that can be used to create unique offspring, so it is not necessary for each daughter cell to differ from the others.