The answer is meiosis.
In meiosis, this process produces 4 daughter cells which are all genetically different to each other and their parent cell. They have only half of the chromosomes. This is because, at one point in the process before the cells divide, parent do not copy their genetic information, which ends up each daughter cells only receiving half of the chromosomes after division.
The daughter cells are also said to be haploid, and in human, these cells are usually gametes, which are for reproduction, so that after 2 of these haploid cells join together, the correct amount of chromosomes can be restored.