The difference between anaphase 1 and anaphase 2 is the separation of different types of chromosomes. In Anaphase 1 of mitosis, the homologous (same) chromosomes separate to either side of the cell, and the centromere is whole. In Anaphase 2, the sister chromatids separate, and the centromere is split, which causes the chromatids to separate.
In anaphase 1, the homologous chromosomes move to the opposite poles, and the sister chromatids remain attached. There are other changes: the kinetochore microtubules (spindles) shorten to pull the chromosomes towards the poles. This forms two haploid sets meaning that each set has 23 chromosomes or 46 total, the number typically found in humans. Each chromosome has two chromatids which move separately in anaphase 2.
In anaphase 2, the centromeres are cleaved down the middle allowing microtubules to attach to the kinetochores which pulls the sister chromatids apart. The centromeres are the center part of the sister chromatids that hold them together, often represented by a dot or a circle. When this is broken, the two separate. The sister chromatids are now called sister chromosomes as they move toward opposing poles and are no longer together. By this time, the cell is almost ready to completely separate into daughter cells, resulting in four overall daughter cells by the end of meiosis 2.