A capsule collection is a short, focused range of pieces that a brand releases alongside its main lines, built around one theme, one season or one famous collaborator, and usually available only for a limited time. Scarcity is the whole point: fewer pieces, longer queues.
The name borrows from the capsule wardrobe, a handful of interchangeable essentials that can be combined into a week of outfits. That idea was popularised in the 1970s by Susie Faux, owner of a London boutique called Wardrobe, although the word capsule, in the sense of small and compact, had been turning up in American publications decades earlier. In 1985 Donna Karan made it fashion news with Seven Easy Pieces, a set of interchangeable workwear items for women. The fashion industry then did what it does best with a sensible, thrifty idea and turned it into a limited edition.