https://en.wikipedia.org/wiki/Purchase_funnel

The purchase funnel, or purchasing funnel, is a consumer-focused marketing model that illustrates the theoretical customer journey toward the purchase of a good or service.

In 1898, E. St. Elmo Lewis developed a model that mapped a theoretical customer journey from the moment a brand or product attracted consumer attention to the point of action or purchase. St. Elmo Lewis' idea is often referred to as the AIDA-model, an acronym that stands for Awareness, Interest, Desire, and Action. This staged process is summarized below:

Awareness – the customer is aware of the existence of a product or service
Interest – actively expressing an interest in a product group
Desire – aspiring to a particular brand or product
Action – taking the next step towards purchasing the chosen product
The purchase funnel is also often referred to as the "customer funnel", "marketing funnel", "sales funnel", or "conversion funnel". The association of the funnel model with the AIDA concept was first proposed in Bond Salesmanship by William W. Townsend in 1924.

This early model has been modified by marketing consultants and academics to cater to the modern customer and is now referred to in marketing as the "purchase funnel" or "buying funnel". Many different business-to-consumer purchase models exist in marketing today, but it is generally accepted that the modern business-to-business purchase funnel has more stages, considers repurchase intent, and takes into account new technologies and changes in consumer purchase behavior. As a model, the buying funnel has been validated in a variety of domains, including searching, keyword advertising, and lead generation, but also modified to include previously unconsidered steps and metrics such as outbound sales, Internet impressions, and Sales Funnel Stages.

The purchase funnel concept is used in marketing to guide promotional campaigns targeting different stages of the customer journey and as a basis for customer relationship management (CRM) programs and lead management campaigns.