Retractable gear
Retractable gear is a UK up-and-over garage door mechanism with springs mounted on both sides of the frame, letting the whole door retract fully inside the garage and handle openings up to around 5m wide.
Because retractable gear supports both sides of the door evenly, it is mandatory on double garage doors and is a far better candidate for adding an operator than canopy gear. It generally costs more than canopy gear but automates more reliably.
UK vs US usage
US suppliers typically describe this only via spring type (torsion vs extension) rather than as a distinct "retractable" gear category — the canopy/retractable split is UK-specific terminology.