Prophase 2 is a stage that occurs in the process of cell division. It begins when the nuclear envelope breaks down and the spindle apparatus is formed as a result. During Prophase 2, the centrioles duplicate during the separation of the pair of chromosomes; which in turn forms two different daughter centrioles that are perpendicular to each original centriole.
To simply put it, this is the process in which a cell breaks down in half to form two new daughter cells that separate into different centrosomes. During this stage, no further replications of chromosomes occur in the cell.