From Yu-Gi-Oh!

Synchro Monsters are the newest type of Monster Card, first released in Starter Deck 2008. The colour of their card frame is white. These cards are included in the Extra Deck.

Synchro Monsters require Tuner Monsters to be face-up on your Field. When the total Level of the Tuner monster and any other face-up monsters on your Field exactly matches the Level of the Synchro Monster you wish to Summon (no more or less); by sending them to the Graveyard, you can "Synchro Summon" the Synchro monster. Some Synchro Monsters require a specific "Tuner Monster" in order to be Synchro Summoned (such as "Junk Synchron" for "Junk Warrior") or monsters of a particular Type or Attribute as Material Monsters, but many do not, so they can be in just about any Extra Deck.

Because Synchro Monsters belong in the Extra Deck, they return there whenever they would be returned to the hand or Main Deck, like Fusion Monsters before.^ref Also, like Fusion Monsters, they cannot be Special Summoned from the Graveyard if they were not properly Synchro Summoned first.

Some players have begun to use the term 'Synchronize' or 'Tune/Tuning' to then list which Tuner Monster and non-Tuner monsters will be sent to the Graveyard when they perform a Synchro Summon and summoning a Synchro Monster ("Tune" is more common, because it's the term used in the TV show). (i.e. "I Tune my 'Quillbolt Hedgehog' [LV2] and 'Speed Warrior' [LV2] with my 'Junk Synchron' [LV3] to Synchro Summon 'Junk Archer' [LV7, requires 'Junk Synchron' as the Tuner]!")

There are currently no Aqua, Fish or Divine-Beast-Type Synchro Monsters in TCG or OCG. However, they have released Synchros for certain Archetypes of monsters, including the Aliens, Iron Chain, XX-Sabers, and Blackwing monsters.

XX-Saber Gottoms is currently the only Synchro Monster that you can use more than 1 Tuner Monster for its Synchro Summon since in its conditions it says " 1 or more EARTH monsters", not "1 or more non-Tuner monster(s)".

Synchro Monsters generally have very powerful effects, especially considering the relative ease of summoning them.

Example

Also see List of Synchro Monsters

See Also: "Synchro Summon".

From Yu-Gi-Oh Card Maker Wiki

Synchro Monsters are a new Type of Monster Cards to be released in Starter Deck 2008. The color of their card frame is white. These cards are included in the Fusion Deck, now called the Extra Deck in the OCG due to Synchro Monsters not being Fusion Monsters.

Synchro Monsters require Tuner Monsters to be Summoned. When the total Level of the Tuner monster and the other monsters on your field matches the Synchro monster's Level, by sending them to the Graveyard, you can Summon the Synchro monster. Tuner Monsters can be Effect Monsters or Normal Monsters.

"Tuner" is the first secondary Type for Normal Monsters.

How to Summon a Synchro Monster

See Also: "Synchro Summon".

Example