An especially attractive date, escort or other companion to a special event. Called "arm candy" because one locks arms with their "candy" (valuable possession) when they enter. A popular connotation of arm candy is a date that someone is using not to enjoy their company, but simply to appear important, wealthy or worthy of attention.
A "golddigger" would likely carry arm candy to a dance or party.
Did you see the arm candy Andrea brought to the dance last night? Her date was so handsome and coy!