In the "web economy" context, the term business model refers to the way an Internet company makes or will potentially make profit.
On the Internet the two ways for generating sales are advertising and ecommerce.
Image source : Ad-Tech-Research-Report-by-Clipperton-September-2012
In digital economy context, business models are often moving and unstable according to the maturity and evolution of a project. Thus it is common that advertising based models drift to paying services models