The spell of oblivion is used by wizards to eliminate memories of the use of magic or to see magical creatures from the mind of Muggles, for this very important reason for the conservation of the magical world all wizards able to successfully perform an oblivion are authorized if you are not obliged to use it on the occasions listed above.
If many people participate in a magical act, experts called Obliviators will be sent by the Ministry of Magic.