Mitosis is the type of cell division that produces new body cells. It is important in three ways.
Growth: a multicellular organism starts as a single cell. Mitosis makes many more cells, so the organism can grow larger. Repair: when tissue is damaged, for example a cut in the skin, mitosis makes new cells to replace the ones that were lost or worn out.
Asexual reproduction: some organisms make new individuals from just one parent, with no gametes involved. The offspring are made by mitosis, so they are genetically identical to the parent. Examples are a strawberry plant growing runners and a yeast cell budding off a new cell.