A Flip Summon, known as a Reverse Summon in the OCG, occurs when a player manually flip a face-down Defense Position monster into face-up Attack Position. A player must Flip Summon to flip his/her own monsters face-up without a card effect. Flip Summons are not considered Normal Summons or Special Summons. A player can Flip Summon as many times as he/she wishes to, as long as he/she has the ability to do so. Flip Summoning is considered manually changing a battle position, thus a player cannot Flip Summon the same monster more than once per turn, nor switch the Flip Summoned monster back to Defense Position without the aide of card effects.
When a Flip Effect Monster is Flip Summoned its Flip Effect will activate. Flip Effects will also activate if the monster is flipped face-up in the Damage Step or if flipped face-up by an effect that does not negate Flip Effects, such as the effect of "Swords of Revealing Light". However, Flip Summon Trigger Effects must be triggered by a proper Flip Summon, not by the card being flipped in any other way.
With cards such as "Stealth Bird" or "Guardian Sphinx", a player can Flip Summon it and use its own effect to flip it face-down again in the same turn. This is possible because of those card's effects and cannot otherwise be done.
A monster flipped face-up by a card effect such as "Book of Taiyou" or "Stop Defense" or as a result of battle is not considered a Flip Summon. Only flipping a Set monster manually is considered a Flip Summon. However, because the monster was flipped face-up, any Flip Effects will activate.