The practice of analyzing the funnel and how many people are dropping off at each stage of funnel in order to improve the marketing performance is known as funnel analysis. For example, in marketing there is a funnel model called AIDA i.e. attention > interest > desire > action. In all 4 stages it is important to keep the customer hooked towards the product/brand so that a successful conversion happens.
The funnel might lose the person if the communication has any loopholes or doesn't sound coherent. For example it is important to communicate the clear value of product in all 4 stages of the funnel. Any mismatch might result in trust issues. To design a successful funnel marketers should understand their target audience properly and what motivates them. They should study buyer persona and take help of available data to make sound behavioral predictions.