Conversions are important to web design and ecommerce. And the conversion funnel is a metaphor that is used to describe how people move from being first time visitors through your site to finally converting into customers of your site.
This process is a funnel because typically a large number of people start out at your site or at an advertisement for your site and they are gradually winnowed down to the small percentage that convert. The typical rate ranges from between 0.1% to 10% depending upon what you're trying to convert - for example, converting a customer used to getting free resources into one who pays for a resource will typically have a much lower conversion rate than a funnel for converting a first-time visitor into a second-time visitor.
