The characters literally combine to mean “Master of the Eastern Road.” This phrase has a fascinating origin from the ancient classic *Zuo Zhuan* (左传). The state of Zheng was located to the east of the powerful state of Qin. When Qin's envoys traveled further east, they passed through Zheng. The ruler of Zheng offered to provide them with supplies and security, thus acting as the “master of the eastern road.” This act of providing for travelers evolved into the modern meaning of “host.”
The concept of the 东道主 is a cornerstone of Chinese social culture and is deeply intertwined with the values of hospitality, generosity, and 面子 (miànzi) (face/social prestige). In Western culture, a “host” can be casual. You can “host” a potluck where everyone contributes, or friends might split the bill at a restaurant even if one person initiated the invitation. In China, the role of the 东道主 is much more defined and carries greater responsibility. The host is expected to be generous and cover the expenses, whether it's for a meal, an event, or lodging for a visiting guest. This isn't just about money; it's about showing respect, sincerity, and building 关系 (guānxi) (relationships). A good 东道主 who provides an excellent experience gains significant “face” and strengthens social bonds. Conversely, failing to be a gracious host can lead to a loss of face for both the host and the guest. This is why at a Chinese dinner, you'll often see people theatrically “fighting” over the bill—everyone wants to fulfill the honorable role of the 东道主.
东道主 is used in both formal and informal contexts, but always implies a clear host-guest dynamic.