Cytokinesis is the essentially the last part of the cell cycle. It is the part where the two new daughter cells are formed. At that stage, animal cells form a contractile ring at the furrow or cleavage. Upon increase of hydrolysis, the cleavage furrow continues to contract inside until the complete separation of the daughter cells.
Plant cell cytokinesis is different. Since there is a presence of cell wall, cleavage furrow is hard to form. Instead, they form cell plate which eventually becomes the cell wall at the middle of the cell that divides the two new daughter cells.
Without cytokinesis, it is impossible for the growth and development of new cells to happen.