gametes are cells used to sexual reproduction. they are haploids and that means they have just one set of chromosomes (most of the cells of our body have 2 sets). that kind of cells is produced mainly by meiotic division of the gamete's stem cell (called oogonium or spermatogonium) and that's why meiosis usually leads to the production of gametes. gametes are haploids so that they could combine (egg with sperm cell) and create the whole new organism (adult organism is almost always diploid).