Also known as: 双喜, 雙喜, 囍, 喜喜, 双喜紋
A type of "auspicious symbol", showing the Chinese character 囍 (double happiness), which is the doubling of 喜 (happiness).
As well as seen in Chinese New Year posts, it's also used at traditional weddings in China, Japan and Korea, as the two individual symbols can symbolize a bride a groom.