Engagement in marketing refers to a consumer making a meaningful interaction with a company’s marketing assets and/or its brand as a whole.
More than simply seeing an ad or a marketing asset, engagement describes a consumer actually interacting with a company’s offering. This can come in a quantifiable sense (clicking “like” or commenting on a post) or it can be more emotional, like a potential consumer being attracted to your company because of the colors or messaging used, then remembering that impact when considering making a purchase later.
Engagement marks a critical component of the marketing mix. It means consumers are interacting with your marketing efforts, and it means your company is embedding itself in their future decisions. After engaging a customer, sometimes in multiple instances over time, your company is more likely to be considered when they are ready to make a purchase — and your company can use the data gained along the way to drive future engagements.
References
https://en.wikipedia.org/wiki/Engagement_marketing