An early adopter is one of a group of people who are the first to embrace a new technology ahead of the general population. They make up roughly 14 percent of the population, according to the Diffusion of Innovation (DoI) theory, which was formulated by communication scholar Everett Rogers. The term is mostly used in regards to consumer technology, and so early adopters are also called lighthouse customers because they serve as a beacon for other customers to follow. Early adopters are the ones who mostly dictate the acceptance of a product for the early majority, the late majority and even for the laggards (the very late adopters).
Techopedia explains Early Adopter
Early adopters are the first consumers to purchase a new product before the majority of the population, and often do so by ordering the product in advance of its launch date. They provide some level of feedback regarding new technology, and are therefore considered trendsetters.
Early adopters may also be people who are given privileged access to technology before it becomes available to the general population. These are the beta testers and product reviewers who, in essence, are in no way connected to the organization creating the technology and whose views are considered to be highly influential when it comes to the commercial success of the technology or the product.