Referral refers to the process of encouraging customers to refer others to a product or service. Referral is a key metric that measures the success of a company's efforts to drive word-of-mouth marketing and viral growth. It is the fifth step in the customer journey, following retention, and is critical for building a successful product.

Referrals are achieved by creating a compelling product experience and encouraging customers to share it with others. This may include features such as referral programs, customer reviews, and social sharing, among others. In order to be successful, companies must understand the target audience and their behavior, as well as the most effective methods for driving referrals.

Measuring and tracking referrals is important, as it provides insights into the effectiveness of word-of-mouth marketing efforts and helps to identify areas for improvement. By focusing on referrals, companies can drive exponential growth and increase revenue, which leads to long-term success and competitiveness. Thus, referrals are a key factor in the success of new product development and marketing, and it is essential to track and optimize this metric as part of a company's overall growth strategy.