Also called the purchase or conversion funnel, the marketing funnel is a well-known and evolving metaphor for a model that suggests interaction with media when perceptions of a brand or business move from general awareness at the level with the largest audience to consideration to preference to relationship to commitment and finally loyalty, with audience size shrinking at each subsequent level. Various media tactics (how you arrange the media buys by potential ROI) play a critical role at each level and most media will overlap by degrees of interaction.
For example, TV, radio or print advertising may (should) include a website URL, telephone number and/or invitation to visit a social media website like Facebook, LinkedIn or Twitter. This changes the fundamental shape of the funnel to have multiple entry points with different subsequent tactics. The end of the funnel has fundamentally changed too, as email and social media have changed the way companies maintain customer loyalty.
Even without explicitly mentioning a website or social media, you can assume that a potential client will first use a search engine to search for the brand name or product/service category from which they will next visit a website or two, or three, or more. It's what shoppers do today, and they're not just doing it on a PC, but are using their mobile devices such as smart phones and digital tablets. The path is no longer linear. Mass media has been fragmented into discrete tactics within discrete channels. Understanding how your customers travel through the multiple channels of today's marketing funnel and how you interact with them is one of the greatest challenges faced.
The following example shows a real campaign with paid search turned on, then off, then back on, and finally having TV advertising added. Imagine these tactics as channels in the marketing funnel. Interestingly, you can see that turning paid search on increases new website visits as expected, but when TV advertising is added to the mix, new website visits dramatically increase, especially with paid search performance and cost.
Rather than wax too prosaically about various marketing funnel models and no doubt increase the amount of text this website has for search engine indexing (like so much of the Internet simply "spins" another's original content), I suggest visiting Marketing-Made-Simple.com for a more complete discussion. What's important here is that the metaphor of the funnel is kept in mind to help build a model that best fits your business. I can help you do this. Here, you can read an interview with me related to this topic, published by B2B online "magazine for marketing strategists" right at the beginning of the economic recession.