竹简, or bamboo slips, are ancient writing materials made from thin strips of bamboo. They were commonly used in China before the invention of paper. The slips were often tied together to form a book-like structure, allowing for the recording of texts, literature, and official documents. These bamboo slips date back to the Warring States period and were an important medium for scholars and officials. Many historical texts, including works by Confucius and Laozi, were inscribed on bamboo slips, preserving knowledge and culture for future generations.