Over the past 12 years, the Internet has changed the way we buy and sell goods and services. Do you remember buying airline tickets before the Internet? Can you imagine buying a new computer or car without doing hours of Web research? And Christmas shopping? You actually had to step foot in the mall…ugh.

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E-commerce has grown; it's estimated that 72 million users shopped online on "CyberMonday," on November 26, 2007.

By definition, e-commerce means the buying or selling of goods and services over the Internet. According to the Pew Internet & American Life Project, 66 percent of the adults online have purchased something over the Internet, whether it's books, shoes or a Caribbean cruise.

But if you extend e-commerce's definition to include researching products and services online without buying anything, or bidding on an online auction but not winning, then the number of adults who participate in e-commerce jumps to 93 percent [source: Pew Internet & American Life Project]. That's just about all of us.

Even with a slumping global economy, online retail sales continue to rise. According to recent forecasts by Forrester Research, online retail sales will increase 17 percent in 2008 to reach an annual total of $204 billion, with the biggest sellers being clothing, computers and cars [source: InformationWeek].

E-commerce's history is short but fascinating. Over the course of a few decades, networking and computing technology have improved at exponential rates. Powerful personal computers linked to global information networks have powered a whole new world of intellectual, social and financial interactions. And this is only the beginning.

How did e-commerce get started? What were the first companies to really capitalize on the selling power of the Web? Read on to find out.