Wikipedia
Xiaochi are an important category of Chinese food, commonly found in ethnically Chinese areas in mainland China, Taiwan, and around the world. Xiaochi are substantial snacks, which could be eaten together or with more substantial dishes like the Spanish tapas or Levantine meze, or alone as a light meal or snack like the French goûter.
Xiaochi are not typically cooked in homes nor are they featured prominently on the menus of more formal restaurants (although a few courses of a multi-course banquet might be xiaochi). Instead, they are street food sold in markets at special stalls or small restaurants that specialize in a few or even just one xiaochi. Night markets are especially known for their specialty xiaochi food items. Here, xiaochi are either served as carry-out or sometimes at small tables with stools for seating. Taiwanese food critic Shu Kuo-chih describes xiaochi as "food from a street stall, shop or even a restaurant that comes in small portions and could never be considered a 'square meal' on its own. In New York, he says, ' hot dogs or nachos could be xiaochi.' Dim sum? Definitely."
Xiaochi are highly local and, in some cases, one city's markets, or even one particular market or restaurant, can become famous for a particular type of food. The city will often become known for that food and the city name be used as an identifier or an attribution of quality (e.g. Chengdu xiaochi in Beijing). Specific types of xiaochi will often change from year to year with passing fads but staples persist.
Xiaochi can often form part of the fourth meal of the day, the xiaoye (宵夜; "supper" or "midnight snack"), a small late evening meal.
Even smaller pre-made side dishes (usually accompanying alcohol or a more substantial meal) are known as xiaocai (小菜, "small dish").