In mitotic division, the chromosome material in the nucleus is replicated. That is because the DNA which makes up the chromosomes can serve as a template to make more DNA. By making a second set of chromosomes during interphase, it will insure that at the end of mitotic division, each new daughter cell will have a full set of chromosomes. This will allow the two cells to carry out life activities and manufacture the proteins they need. After interphase, prophase occurs. The centrioles separate and a spindle begins to form.The nuclear membrane begins to disappear and the chromosomes are coiled and thickened. Next is metaphase. In this stage, the doubled chromosomes, called chromatids line up along in the equator of the cell. Their centromeres in the center attach to the spindle fibers that have formed. Next is anaphase. The doubled chromosomes separate and they move toward opposite poles. Next is telophase. The cell membrane pinches inward forming two separate cells. The nuclear membrane reforms in each new cell enclosing the chromosomes. If its an animal cell, cytokinesis occurs and the cell pinches in half. End result is two daughter cells, with the exact chromosome number as the parent cell. If it is a plant cell, a cell plate forms separating the two cells. And cytokinesis insures that half of the cytoplasm goes to each smaller but genetically identical cell.
Mitosis is defined as the type of cell division by which a single cell divides in such a way as to produce two genertically identical "daughter cells". This is the method by which the body produces new cells for both growth and repair of aging or damaged tissues throughout the body - as opposed to for sexual reproduction (when meiosis applies).
Mitosis is the simplest of the two ways (mitosis and meiosis) in which the nucleus of cells divide - as part of a process of cell division.