Both meiosis and mitosis are types of nuclear division. The main difference between the two is the number of nuclear divisions that take place:
Mitosis: involves one nuclear division which produces two daughter nuclei with the same number of chromosomes as the parent cell nucleus and each other. Mitosis therefore results in each of the two daughter cells having a nearly exact copy of the DNA of the parent cell. The daughter cells are diploid.
Meiosis: involves two nuclear divisions, one after the other. These are Meiosis I and Meiosis II. Meiosis therefore results in the formation of four daughter nuclei, each with half the number of chromosomes of the parent cell. The four daughter cells are haploid cells.