1) Goods and Services Tax (GST) is a value-added tax introduced in India in 2017 that replaced existing multiple taxes levied by the central and state governments. 2) GST aims to create a common national market by eliminating cascading taxes and promoting India as a single market. 3) Key concepts of GST include the Integrated GST (IGST) for inter-state trade, a destination-based tax instead of origin-based, and a compliance rating system. GST also established a rare example of cooperation between the central and state governments through the GST Council.