Typically this will be a customer who, in addition to using the vendor's product or technology, will also provide considerable and candid feedback to help the vendor refine its future product releases, as well as the associated means of distribution, service, and support.
The relationship is synergistic, with the customer having early (and sometimes unique, or at least uniquely early) access to an advantageous new product or technology, but he or she also serves as a kind of guinea pig.
In exchange for being an early adopter, and thus being exposed to the problems, risks, and annoyances common to early-stage product testing and deployment, the lighthouse customer is sometimes given especially attentive vendor assistance and support, even to the point of having personnel at the customer's work site to assist with implementation. The customer is sometimes given preferential pricing, terms, and conditions, although new technology is often very expensive, so the early adopter still often pays quite a lot.
The vendor, on the other hand, benefits from receiving early revenues, and also from a lighthouse customer's endorsement and assistance in further developing the product and its go-to-market mechanisms. Acquiring lighthouse customers is a common step in new product development and implementation. The real-world focus that this type of relationship can bring to a vendor can be extremely valuable.
Early adoption does come with pitfalls: early versions of products may be buggy and/or prone to malfunction. Furthermore, more efficient, and sometimes less expensive, versions of the product usually appear a few months after the initial release (Apple iPhone). The trend of new technology costing more at release is often referred to as the "early adopter tax".