How and when are supererogatory prayers (Salat al-Nawafil) performed?

Supererogatory prayers (Nawafil) are performed like obligatory prayers in terms of conditions, pillars, and duties. However, they are valid when performed by one sitting without an excuse, and on a mount during a journey where shortening prayers is permissible, without facing the Qiblah at that time.

The times for performing them vary according to their types. They are permissible at all times except during the forbidden times. It is best to pray them two rak'ahs by two rak'ahs. It is sunnah (definition) for the supererogatory prayers of the day to be silent and for the supererogatory prayers of the night to be audible.