E-Commerce refers to buying and selling online, while E-Business encompasses all business conducted online.
E-commerce can be viewed as a subset of e-business. If you plan on starting or working closely with an internet-based company, you should strive to understand all the ways these two concepts are unique.
E-Business refers to performing all types of business activities through online and at the same time having a physical store while E-Commerce refers to the businesses that doesn't have any physical stores, warehouse or shops that's existing and eventually use electronic means for business transactions.
Every small business has a supply chain, the network of vendors that provide the raw components that are needed to make a product or deliver a service.
SCM is about efficiently and effectively improving the way that a company finds those raw components and then delivers the product or the service to the customer.