A Tribute Summon (Japanese: アドバンス召喚Adobansu Shōkan "Advance Summon") is a form of Normal Summoning a Level 5 or higher monster by Tributing another monster(s) you control. Level 5 and 6 monsters require one Tribute, while Level 7 and higher require two Tributes.
Tributing a monster for a Tribute Summon is part of a Summoning condition. Therefore, if the Tribute Summon is negated, the Tributed monster(s) will not return to the field.
Some cards require 3 Tributes to be Normal Summoned, such as "The Wicked Avatar". Other monsters can be Tribute Summoned with varying numbers of monsters, such as "Moisture Creature".
Some cards allow high-Level monsters to be Normal Summoned with fewer or no Tributes. "Fog King" can be Tribute Summoned with 1 Tribute, or Normal Summoned without a Tribute. "Mausoleum of the Emperor" allows either player to payLife Points instead of Tributing monsters. However, if no cards are Tributed to perform the Normal Summon (as in the case of "Mausoleum of the Emperor"), the Summon is not a Tribute Summon, unless a card specifies otherwise (such as "Tribute Burial").