The silk road refers to overland trading routes between China and the West, not to a single road. Several routes of trade originated in China's Chang'an (today's Xian) moving on either northern or southern routes. Northern routes moved from China to Iran, Iraq, Syria, and Turkey. Southern routes moved silk to South East Asia, India; from India to East Africa, then north through the Red Sea to Greece.
Silk was found in an ancient Egyptian tomb dated to 1070 BCE (BC). The oldest example of silk is from 3630 BCE. First limited to the Chinese emperor and his family, the fabric became a valuable trading commodity and well-kept secret. In 550 CE (AD) silk moth eggs were smuggled from China to the Emperor Justinian of the Byzantine Empire, the last stronghold of the Roman Empire. Byzantium weavers were unable to produce high-quality silk made in China. Silk is a fine, smooth fabric that was worn by the elite due to its cost.
Silk was ideal for trade due to its value and ease of transport. Other goods moved from east to west included porcelain, spices, jade, paper, and gunpowder. Wool was moved east and included rugs, fabrics, and blankets. Various goods would be traded along the way including silver, gold, ivory, and bronze.
Ideas spread along the trade route as well including philosophies, religions, science, arts, and crafts. When the Ottoman Empire closed northern trade routes in 1453, Europe took to the seas for trade.