Special Summon Monster
The OCG Rulings refer to both Special Summon-only monsters and Nomi monsters as Special Summon Monsters. These monsters cannot be Normal Summoned or Set.
Usually, a Special Summon Monster has a condition that restricts how the monster must be Summoned. Other than by this condition, the Special Summon Monster cannot be Special Summoned from the hand/Deck. The condition is almost always a Summoning Condition, so the monster can only be Special Summoned from the hand. Also, such a monster cannot be Special Summoned from Graveyard/Banished Zone unless it was properly Special Summoned beforehand via its condition - this last restriction is a game mechanic, and cannot be ignored by cards that ignore Summoning Conditions.
Alternately, a Normal Summon Monster is a monster without these restrictions. A Normal Summon Monster may be Normal Summoned or Set, and usually can be Special Summoned from the hand/Deck/Graveyard/Banished Zone by other card effects.
Some Normal Summon Monsters - like "Cyber Dragon" or "Red-Eyes Darkness Metal Dragon" - have an additional Summoning Condition that allows you to Special Summon it. In this case, the monster may still be Special Summoned from the hand/Deck by other effects, and may be Special Summoned from the Graveyard/Banished Zone regardless of whether the monster was "properly" Special Summoned beforehand.
