These characters combine to literally mean “buy east west.” The most popular theory for this origin dates back to the Tang Dynasty (618-907 AD). The capital city, Chang'an, had two massive, designated markets: the East Market (东市) and the West Market (西市). The East Market sold goods for the wealthy, while the West Market sold everyday goods for the common people and exotic items from the Silk Road. To go “buy from the east and west” markets was to do all of one's shopping. Over time, 买东西 became the general term for buying anything, anywhere.
While “shopping” is a universal activity, 买东西 is deeply embedded in the rhythm of modern Chinese life. It encompasses a vast range of experiences, from haggling for fresh vegetables in a noisy, vibrant wet market (菜市场 - càishìchǎng) to scrolling through massive e-commerce platforms like Taobao and JD.com on a smartphone. In Western culture, a similar phrase might be “to run errands.” However, “running errands” can include non-purchasing activities like going to the post office or dry cleaner. 买东西 is specifically about the act of purchasing goods. Furthermore, shopping in China is often a highly social activity. It's common for friends, couples, or families to spend a weekend afternoon going to 买东西 together at a large shopping mall. This is less about necessity and more about leisure and social bonding, often combined with a meal or a movie. The rise of digital payments like WeChat Pay (微信支付) and Alipay (支付宝) has revolutionized the process, making the act of paying for things instantaneous and a seamless part of the 买东西 experience.
买东西 is primarily a conversational and informal term. You'll hear it constantly in daily life.