Retention refers to the process of keeping customers engaged and using a product or service over time. Retention is a key metric that measures the success of a company's efforts to build customer loyalty and maintain a strong customer base. It is the fourth step in the customer journey, following activation, and is critical for building a successful product.

Retention is achieved by providing ongoing value to customers through features such as new product releases, updates, and customer support. In order to be successful, companies must understand the target audience and their evolving needs, as well as the most effective methods for retaining customers over time.

Measuring and tracking retention is important, as it provides insights into the effectiveness of customer engagement and loyalty efforts and helps to identify areas for improvement. By focusing on retention, companies can reduce customer churn and maintain a strong customer base, which leads to increased revenue and long-term success. Thus, retention is 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.