PURPORT

This verse explains why the Supreme Personality of Godhead appears as an incarnation again and again. The incarnations of the Supreme Personality of Godhead all function differently, but their main purpose is paritranaya sadhunam vinasaya ca duskrtam-to protect the devotees and annihilate the miscreants. Yet even though the duskrtis, or miscreants, are annihilated, this is ultimately good for them.