Customer Retention is the work of keeping existing customers engaged, satisfied, and willing to buy again or continue using a service.
It matters because strategy keeps channels from competing with each other. When this concept is clearly defined, the team can connect budget, audience, creative, offer, tracking, and reporting to revenue instead of chasing disconnected metrics.
Example
A subscription business reviews why customers leave, improves onboarding, and offers useful support before renewal. Customer retention focuses on sustaining the relationship; it is not measured simply by sending more messages to existing customers.