Mitosis is simply the division if cells.
It has five different stages.
Interphase - cell performs all its normal functions. Before mitosis begins, DNA doubles.
Prophase - DNA contracts and nucleus wall disappears
Metaphase - Spindle is visible and helps chromosomes line up on equator
Anaphase - Chromatids get pulled to opposite poles.
Telophase - the two nuclei reform around the DNA. The cells divide (cytokinesis)