Because a Webinar room allows you to communicate with your customers and employees better, and to get feedback from them at the right time, with the right information. This happens because a Webinar room allows you to enter a virtual conference room, talk (in your voice) and share pictures, web sites, Power Point Presentations and in some cases, any application on your computer, such as Excel, Word, etc. to tell a story or show people why they need your product or service.
A trademark for the term WEBinar (first three letters capitalized) was registered in 1998 by Eric R. Korb (Serial Number 75478683, USPTO) and was reassigned to InterCall. The trademark registration was cancelled in 2007. Learn.com filed a claim for the term "webinar" without regard to font or style in 2006 (Serial Number 78952304, USPTO). That trademark claim was abandoned in 2007 and no subsequent filing has been made.
Create a presentation you can deliver which is related to that product. The presentation should be helpful and useful, and mostly pure content. If the webinar is going to be an hour long, then you should have at least 45-50 minutes of good, solid content in there before you ever even talk about the product. An exception would be if the entire point of the webinar is how to use that product.
To attract more participants, you can start from some free webinars for certain times. Once you can get webinars well prepared, run webinars interactively and show the great value of your webinar, more and more participants will be willing to pay for your entire webinars and then it's a good chance to create paid webinars to monetise your expertise.
Web conferencing may be used as an umbrella term for various types of online collaborative services including web seminars ("webinars"), webcasts, and peer-level web meetings. It may also be used in a more narrow sense to refer only to the peer-level web meeting context, in an attempt to disambiguate it from the other types of collaborative sessions. Terminology related to these technologies is inexact, and no generally agreed upon source or standards organization exists to provide an established usage reference.