Ecommerce (electronic commerce) is the buying and selling of goods and services on the Internet, especially the World Wide Web. In practice, this term and a newer term, eBusiness, are often used interchangeably. Ecommerce (e-commerce) or electronic commerce, a subset of ebusiness, is the purchasing, selling, and exchanging of goods and services over computer networks (such as the Internet) through which transactions or terms of sale are performed electronically. Ecommerce can be broken into four main categories: B2B, B2C, C2B, and C2C.

B2B (Business-to-Business)
Companies doing business with each other such as manufacturers selling to distributors and wholesalers selling to retailers. Pricing is based on quantity of order and is often negotiable.

B2C (Business-to-Consumer)
Businesses selling to the general public typically through catalogs utilizing shopping cart software. By dollar volume, B2B takes the prize, however B2C is really what the average Joe has in mind with regards to ecommerce as a whole.

C2B (Consumer-to-Business)
A consumer posts his project with a set budget online and within hours companies review the consumer's requirements and bid on the project. The consumer reviews the bids and selects the company that will complete the project. Elance empowers consumers around the world by providing the meeting ground and platform for such transactions.

C2C (Consumer-to-Consumer)
There are many sites offering free classifieds, auctions, and forums where individuals can buy and sell thanks to online payment systems like PayPal where people can send and receive money online with ease.