超市(chāo shì) - supermarket in Mandarin

超市 (chāoshì) is the supermarket, a shortened form of 超级市场 (chāojí shìchǎng), "super market" borrowed almost word for word from English and then trimmed down for everyday speech. 超 (chāo) means "super, to exceed" and 市 (shì) means "market, city", so the short form still carries the original sense even once you drop 级 (jí) and 场 (chǎng).

It is the default word for a mid-to-large grocery store, as opposed to 便利店 (biànlìdiàn), a small convenience store, or 市场 (shìchǎng), a traditional market, often outdoors and selling fresh produce. "One supermarket" is 一家超市 (yì jiā chāoshì).

去超市 (qù chāoshì), "to go to the supermarket", is one of the most common short phrases a beginner will use, so it is worth drilling alongside 买东西 (mǎi dōngxi), "to buy things", which very often follows it in the same sentence.