Meiosis is a process of cell division that specifically creates sex cells.
In the first stage of meiosis, meoisis I, the DNA in a cell is arranged into chromosomes, duplicated, and then split between two new cells.
In meosis II, these two cells divide again into two more cells each. These cells, called haploid cells, only have a half set of DNA to ensure genetic variation in offspring.
If you had 3 cells undergo meiosis, they would produce 4 haploid cells each, for a total of 12 haploid cells.