1. Engagement refers to the level of interaction and commitment customers have with a brand, and can be measured through behaviors like email opens, clicks, and transactions. 2. Customer engagement is important because highly engaged customers are more loyal and profitable, acting as brand advocates who increase revenue and market share through referrals. 3. Measuring and quantifying customer engagement through profiling algorithms allows companies to better understand customers, customize campaigns, and reconnect with less engaged customers, helping to drive business goals like increased revenue and stronger customer relationships.