'卖东西' literally combines '卖' (to sell) with '东西' (things, stuff, merchandise), forming a common verb phrase meaning 'to sell things' or 'to sell goods'. While '东西' alone can mean 'thing(s)' in a general sense, in this compound it specifically refers to items intended for sale — not abstract concepts or people. The phrase is neutral in register and widely used in everyday spoken and written Chinese, especially when describing small-scale or informal selling activities like street vending, flea markets, or online resale.

Grammatically, '卖东西' functions as a transitive verb and often appears with objects (e.g., 卖东西给顾客), duration complements (e.g., 卖了三年东西), or aspect particles like 了 or 着. It’s rarely used in formal business contexts where terms like '销售商品' (to market goods) are preferred. The phrase emphasizes the action of selling tangible items rather than services or intangible assets.