A conversion funnel is a marketing term used to describe the progression of someone going from being a stranger to becoming a customer. It is often shown as a triangle with three sections: top (acquisition), middle (conversion) and bottom (retention).
The purpose of the funnel is to show how the number of customers decreases as they progress down the funnel. The top section represents people who are unaware of your product or service, and those people will generally not be interested in what you have to offer. The middle section, conversion, shows how many people are interested in your product or service but do not make it all the way through. This usually happens because they do not need what you offer or they find another company that offers it better value for money. The bottom section shows how many customers remain loyal and continue to buy from you over time.