The process of formation of sperms is called Spermatogenesis. In this process spermatozoa are produced from male germ cells by way of mitosis and meiosis. The initial cells in this pathway are called spermatogonia, which yield primary spermatocytes by mitosis.
In humans, spermatogenesis takes place in the seminiferous tubules, which are an intricate system of tubules in the testes where spermatogenesis takes place. The seminiferous tubules of an adult human male can sometimes produce over 100 million sperm per day.
The germ cells that are found in the testes are called spermatogonia. Every day, somewhere around 25 million spermatogonia enter meiosis and become primary spermatocytes. After the first meiotic division, the cells double in number and are called secondary spermatocytes. Once the second meiotic division is completed but before the haploid cells have had a chance to differentiate into actual sperm, the cells are called spermatids. These spermatids now have the correct number of chromosomes to be functional gametes, but they don't have the physical characteristics of sperm that allow them to swim to the ovum and fertilize it.