It is a statement that you are willing to partner with a person for life, both physically and spiritually. The wedding band tradition, while it doesn’t go as far back, is still old.
Wedding bands were a thing as far back as the time of the Egyptians, but they only became popular once the Romans discovered metal crafting. Bands of silver or gold became a traditional gift to new brides crossing the threshold, with the circle of the ring standing for eternal and never-ending love.
In Europe, around the medieval period, things started to get more lavish. People getting married started exchanging gold bands, which were sometimes studded with gemstones. The custom of interlocking bands also started around this time.
Things have advanced in the ring arena, and these days, you find diamond wedding rings worn alongside engagement rings. Where in the past, only brides had rings, nowadays both the groom and bride get one, such as a 1 carat cluster diamond ring. This mainly has to do with shifting attitudes regarding equality.