Tribute Summon

Monster that are Level 5 or 6 require one monster to Tributed, and Level 7 or higher cards require 2 monsters to be Tributed, unless Special Summoning Conditions change that. This is known as a "Tribute Summon".

Even if the monster is Tribute Set instead of Tribute Summoned, the correct number of Tributes must still be offered. So a player cannot Set a monster in order to avoid offering a Tribute.

A Tribute Summon is treated exactly as Normal Summon, except a few card effects refer specifically to whether or not the card was Tribute Summoned. Only one Tribute Summon can be conducted in the same turn, unless you have Ultimate Offering in play. This means you cannot Normal Summon or Set a Low Level monster, and then Tribute it immediately to Tribute Summon a High Level one.