Mitosis is when a cell splits into two cells by replicating their DNA, lining them up at the cell's equator and pulling the sister chromatids apart. This creates two identical cells.
http://library.thinkquest.org/C0118084/Gene/Chromosomal_Inheritance/StagesMitosis.htm
Meiosis is when a cell replicates their DNA much like in mitosis except now homologous chromosomes line up together at the equator instead of independently. The homologous chromosomes are then pulled away from their pair and to opposite sides of the cell creating two cells with only half of the total number of chromosomes. These are called gametes. The gametes then undergo mitosis to separate the sister chromatids.
http://faculty.stcc.edu/BIOL102/Lectures/lesson9/stepbystep.htm