Customer engagement is an interaction between an external consumer/customer (either B2C or B2B) and an organization (company or brand) through various online or offline channels.
Online customer engagement is qualitatively different from offline engagement as the nature of the customer's interactions with a brand, company and other customers differ on the internet. Online customer engagement is a social phenomenon that became mainstream with the wide adoption of the Internet in the late 1990s, which has expanded the technical developments in broadband speed, connectivity and social media. These factors enable customer behaviour to regularly engage in online communities revolving, directly or indirectly, around product categories and other consumption topics. This process leads to a customer's positive engagement with the company or offering, as well as the behaviours associated with different degrees of customer engagement.
source