Short answers, pulled from the story.
Trade is the transfer of goods and services from one person or entity to another, often in exchange for money. Economists refer to a system or network that allows trade as a market. Trade between two traders is bilateral, while trade involving more than two is multilateral.
Recent research finds early humans developed trade networks for obsidian 15,000 years ago and for ostrich egg shell beads 50,000 years ago. Trade in obsidian is believed to have taken place in New Guinea from 17,000 BCE, and networks existed around 12,000 BCE.
Trade exists between regions because different regions may have a comparative advantage, perceived or real, in producing certain trade-able goods. It also arises from specialization and the division of labor, where individuals and groups concentrate on a small aspect of production and trade their output for other needs.
Portuguese explorer Vasco da Gama pioneered the European spice trade in 1498 when he reached Calicut after sailing around the Cape of Good Hope. Before this, the flow of spice into Europe from India was controlled by Islamic powers, especially Egypt.
In 1776 Adam Smith published An Inquiry into the Nature and Causes of the Wealth of Nations, which criticized Mercantilism and argued that economic specialization could benefit nations as much as firms. He considered all rationalizations of import and export controls dupery.
The Maritime Jade Road was an extensive trading network connecting areas in Southeast and East Asia, built around jade mined in Taiwan and processed mostly in the Philippines. It existed for at least 3,000 years, peaking from 2000 BCE to 500 CE, making it older than the Silk Road.
The European Union lifted barriers to internal trade in goods and labour in 1992, the North American Free Trade Agreement took effect on the 1st of January 1994, and the World Trade Organization was created on the 1st of January 1995 to facilitate free trade. The Central American Free Trade Agreement was signed in 2005.