"Synchro" (シンクロ Shinkuro) is an archetype of cards related to Synchro Monsters. They appear most frequently in the Yu-Gi-Oh! 5Ds anime and manga, although a few also appear in the Yu-Gi-Oh! ARC-V anime.
Most "Synchro" cards are Spell/Trap Cards that support Synchro Monsters, although there are few exceptions, such as "Synchro Boost" (which increases the equipped monster's Level, facilitating a Synchro Summon). There are also a few "Synchro" monsters, but they are infrequent.