Source: Yugioh Wikia
A Special Summon is a Summon that is performed through the effect of a single card. Special Summons do not use up your 1 Normal Summon or Set for the turn, and can be conducted as many times as possible in a turn and if generally referred to, a monster can be Special Summoned in face up ATK or DEF position, unless indicated by the card. Also, Special Summons can be activated during either player's turn.
"Premature Burial", "Call of the Haunted", "Monster Reborn", "Soul Resurrection", and "Autonomous Action Unit" can all Special Summon monsters from the Graveyard. Thus, you can activate each card (provided you have enough Life Points) and resurrect five monsters, as well as conduct a Tribute Summon or Tribute Set in the same turn.