A traditional Jewish marriage is legally two separate stages, kiddushin, the betrothal that formally sets a couple apart for one another, and nissuin, the marriage proper that completes the union, and for much of the ancient and early medieval period these were genuinely separate events, commonly held as much as a year apart, during which the couple were legally bound to each other yet not yet living together as husband and wife.
Over the medieval period, for reasons connected to the practical and social difficulties of maintaining that long intermediate status, the two stages were drawn together into a single ceremony held on one day, and the chuppah is the structure under which that consolidation is physically expressed: the earlier part of the modern ceremony enacts kiddushin, and the couple's standing together under the canopy for the concluding blessings enacts nissuin, so that a single canopy now visually marks the completion of what was once a year long legal process compressed into one afternoon. The canopy's symbolism reaches further back than the ceremony's current form: reading it as the tent of the patriarch Abraham, open on every side to travelers, extends a specific biblical association with hospitality onto a structure whose more immediate practical ancestor was, in various historical periods, literally the groom's own home or tent, the couple's new shared dwelling represented rather than merely symbolized.