Both mitosis and meiosis are types of cell division. Most of the cells in your body have two full sets of chromosomes: one from your mum and one from your dad. When these cells divide for growth and repair, the parent cell makes a full copy of its genetic code before splitting in two, giving two full sets of chromosomes to each daughter cell.
This type of cell division is called mitosis. However, there are two types of cell that only need one full set of chromosomes: sperm and eggs. When these cells are being made, the parent cell splits into four, and each gets just one set of chromosomes. This is meiosis.