A customer insight, or consumer insight, is an interpretation of trends in human behaviors which aims to increase the effectiveness of a product or service for the consumer, as well as increase sales for the financial benefit of those provisioning the product or service. There is an overlap between market research and customer insights. While market researchers can produce consumer insights, not all insights require market research techniques. The insights industry incorporates competitive intelligence, customer insights, big data, machine learning, social media listening, geomarketing, and text analytics, among other services.
Specifically, consumer insights is a field that focuses on analyzing market research and acting as a bridge between Research and Marketing departments within a company. Commonly referred to as CI, it is the intersection between the interests of the consumer and the features of a brand. Its main purpose is to understand why the consumer cares for the brand as well as their underlying mindsets, moods, motivation, desires, aspirations, that motivates and trigger their attitude and actions.
This latter definition is explained further in an article by Paul Laughlin for the Institute of Direct & Digital Marketing's Journal.
The author emphasises four components of this definition: First, such insight is “non-obvious”, so it does not normally come from just one source of information and often does not come from just analysis or just research; rather there is a need to converge evidence to glean insights. Second, true insights need to be “action-able”; hypotheses that stay theoretical and cannot be tested in practice are not insights. Third, customer insights should be powerful enough that when they are acted upon customers can be persuaded to "change their behaviour". Just benefitting from targeting based on analysing past behaviour and assuming people will be creatures of habit does not reveal any depth of understanding them, certainly not insight. Fourth, to be sustainable, the goal of such customer change must be for "mutual benefit". As  argues, a key law for marketing today is “earn and keep the trust of your customers”, which is achieved by acting in their best interests as well as the long term value for the organisation.
The above components only cover the scope of customer analysis or marketing analysis. Best practice is now expanding to including customer data management, behavioural analysis, predictive analytics, consumer research and database marketing.