Mitosis, dividing of the nucleus... ?

You are correct; all cells undergo mitosis exept gametes, which undergo meiosis. Mitosis is the division of the nucleus, which contains all of the genetic material. The chromosomes (42 for humans) replicate into two sister chromotids. Once the process of mitosis is complete, the result is two identical daughter cells. Meiosis involves crossing over, which maintains genetic variation. In this process, two logous chromosomes come together and they each exchange part of the genetic material. Meiosis results in four new cells that are not gentically identical. Meiosis also only has half of the chromosomes than the body cells have, so that when the male and female gametes come together, the offspring will have the normal amount of chromosomes. This is what seperates mitosis from meiosis.