Web- facilitated viral ,What is it?

Web - facilitated viral ( e-mail prompt). The e-mail includes a link or graphic with 'e-mail a friend' or 'e-mail a colleague 'in a web page. Company is useful to collect visitor's e-mail and then forward  and sometimes with optional message. The company then send a separate message to the friend or colleague.

That's mean when you visit a website which you found something interest or useful, you can write down your friend or colleague's email  with a button with 'e-mail a friend'. Therefore, company can depend on the e-mail address and then send the separate e-mail as forward to your friend or colleague. It is useful for company to collect e-mail address for their database.

Reference: 
Viral Marketing (2011). Retrieved July 12
From Internet Marketing, Strategy,Implementation and Practice (fourth edition)