Today is a world which is driven by technology. GST accounts for it and therefore it provides a separate mechanism to tax those supplies which are made via technology medium. 

For this purpose, there is a definition of electronic commerce under GST law, which basically means supplies which are transacted via an electronic network. In these cases, the person who is managing that technology medium is called an ECO or an Electronic Commerce Operator. 

There are certain obligations which flow upon a ECO, which are in addition to the normal GST obligations. The ECO is required to monitor all the supplies made on the medium even though the ECO himself is not the supplier. 

For eg. Amazon, Flipkart. Amazon or Flipkart do not sell or supply the goods by themselves, they only provide a technology medium. The technology medium ensures that there is a supplier, there is a consumer and they interact through this medium. 

Therefore, if I as a customer go on Amazon and through the platform, book an order for certain supplies, there will be a supplier who will provide me those goods via the technology platform. So in this case, while I am the recipient and there is someone else who is the supplier, Amazon or Flipkart in this case get involved for GST obligations as an ECO, namely the Electronic Commerce Operator. 

ECO is required to file returns and also other compliances as per GST law.