咸菜 is a category, not one specific dish: any vegetable preserved in salt - most often Chinese mustard greens (
雪里蕻,
雪菜), cabbage, radish, or cucumber. It's a staple side dish for breakfast
稀饭 (congee) and
馒头 (steamed buns), and a humble symbol of frugal home cooking. Compare
泡菜 (pàocài) which can mean either Sichuan brined vegetables or Korean kimchi.
