Before entering mitosis or meiosis, DNA contained in a cell duplicates and and each chromosome will have two sister chromatids.
In mitosis the sister chromatids separate to produce two daughter cells that have the same information as the original cell before the DNA duplicated.
On the other hand, meiosis consists of two cell divisions. During meiosis I, homologous chromosomes separate, producing two daughter cells that have half the information the original cell had, but each chromosome still has two sister chromatids. During meiosis II, the sister chromatids separate, and each daughter cell produces two more daughter cells, that now have a single homologous chromosome of the pair, and which has a single chromatid.
