sunken courtyard and courtyard legend

Quick answer：

A sunken courtyard, also known as an underground courtyard, is a traditional Chinese architectural feature where a courtyard is situated below ground level. It often includes a raised platform or a stepped entrance. A courtyard legend, on the other hand, typically refers to a diagram or illustration showing the layout of a courtyard, including its architectural elements and spatial organization. These legends are used to plan and visualize courtyard designs in traditional Chinese architecture.