What it is, briefly
A binding,
literal and symbolic.
A handfasting is a ritual in which the celebrant ties a cord around the wrists of the couple — usually a single wrap and a knot, often with the couple's right hands clasped — at the moment of the vows. The cord remains tied for the rest of the ceremony, or is untied as part of the final blessing. Either way, the couple keeps the cord afterwards.
The ritual is ancient. It appears in Scottish, Irish, and Welsh wedding traditions from at least the medieval period, and likely earlier — predating the Christian church's involvement in marriage in much of the British Isles. For centuries in Scotland, a handfasting was the marriage; couples were considered married for a year and a day after a handfasting, and could either renew the bond or part ways at the end of the year. The Church absorbed the ritual rather than replacing it; many Scottish church weddings retained the handfasting in some form well into the modern era.
For modern couples in Virginia, the handfasting is most often added to an otherwise contemporary ceremony — Scottish, Christian, secular, interfaith. It is the ritual that gives the abstract word "vows" a physical form.