Meiosis is a process which takes place in sex cells (sperms/eggs) where a single cell divides twice to produce four cells containing half the original amount of genetic information.
Anaphase I is a part of meiosis I, first cell division in which homologous chromosomes are pulled towards opposite poles of the cell by the spindle fibres. The sister chromatids of each chromosome, however, remain attached to one another and don't come apart.