The heyday of the silk road is a rather nebulous term, since there has been trade from China, through Central Asia, to the Middle East, Africa, and Europe since Roman times (and even earlier!). Also, there was never one silk road, with many routes over land and sea connecting many areas of Eastern and Central Asia, as well as the Middle East, Africa, and Europe.

As the name suggests though, silk was a major trade good, but many other things travelled long (and shorter) distances. Spices from India and Indonesia and the Philippines, ivory, precious stones from Central Asia, horses from the steppe were particularly sought after in China, paper and eventually paper making technology from China, lacquered items from China, gold, silver, animals (like giraffes!).

Then there are the less tangible, but arguably more important things. Knowledge, stories, technology, philosophy, and religion moved rapidly and extensively. Metalworking technologies, paper making, architectural techniques, and engineering systems were all moving around. Scholars would travel around, particularly during the early Islamic period, learning and collecting knowledge. As the secret to paper making moved out of China, this accelerated, with people writing books collating knowledge from disparate parts of the world, as well as translating classical writings from Europe and India. For example, Ibn Sina (also known as Avicenna) translated and collated classical medical knowledge, and then added his own studies.

Religions and philosophies travelled extensively around Central Asia, with Buddhism, Christianity, Judaism, and Islam being the most widely known.

People also moved around following the silk routes. Missionaries, mystics, traders, and explorers moved around the area, but also slaves were traded along these routes.

Today, one could still argue that electronics, oil, and clothing are still traded along the silk route, with Western cultures looking to the East for important goods and technologies!

I found Peter Frankopan's The Silk Roads to be a wonderfully comprehensive introduction to the way trade between East and West has changed and impacted our world.