Pendulum (archetype)
"Pendulum" (ペンデュラム, Pendyuramu) is an archetype consisting of Pendulum Monsters and cards that support them. This archetype contains two sub-archetypes, "Pendulum Dragon" and "Pendulumgraph".
"Pendulum Machine" is not a "Pendulum" card, because it does not have 「ペンデュラム」 in its Japanese name. However, because support for this archetype only works on Spell/Trap Cards and Pendulum Monsters in the Main Deck, this is not an issue.
Playing style
The archetype is universally supported by "Duelist Alliance", which can search any Spell/Trap or a Pendulum Monster from this archetype. While most "Pendulum" cards generically support various aspects of all Pendulum Monsters, some cards like "Pendulum Call" and "Dragonic Pendulum" only support specific archetypes.