Define E-Commerce? Discuss The Benefits And Risk Of E-Commerce.

E-commerce is the transaction done online to purchase some facility or product by credit card or pay pal. There are many benefits of e-commerce and also has some drawbacks. For details, visit the following link.
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There are lots of advantages of E-commerce and the most important is achieving the world's market. Everything is available to get through the internet.
As to the risks...depends on what kind of risks we are talking. There commercial risks to lose money, to lose customers and so on, but there are others - we can't divine now.
I like what author said in this article
www.articletrader.com/society/what-is-e-commerce-going-to-do "A human often comes a victim of his own inventions as it was with Marie
Curie who had created radium and died from aplastic anemia. Nowadays we
all suffer from  nuclear power plants which causes great damages for the
whole regions in case of emergencies (Chernobyl and Fukushima
disasters, for example)."
May be there are some risks we just aren't able to see now.

E-commerce short for electronic commerce, E-commerce refers to the buying and selling of goods and services or the transmitting of funds or data, over an electronic network, primarily the Internet. There are a few primary modes of e-commerce. Online retail is where an entity of goods for sale over websites. It is the coordination of web technologies such as electronic funds transfer, supply chain management, online transaction processing, inventory management systems, and automated data collection systems. 

Some Pros and cons of E-Commerce are:

Pros-  Cost Effective, Higher Margin, Better Productivity, Economy Benefit.

Cons-  Scalability of System, Security, Integrity on Data and System, Customer Service and Relation Problem.