A minisite, sometimes called a microsite, or sitelet, is a small website that that exists for the purpose of marketing a company's specific product, service, event or promotion.
It typically consists of around 3-5 pages though it may be as simple as a single webpage or as many as twenty pages. (‘Microsite’ may refer specifically to a minisite that only contains one page.)
A minisite usually has its own identity and URL but is linked to a larger website. For example, a gallery’s Web site may have a link to a microsite with information about a special exhibition the gallery is running.
The minisite should be user friendly, enhanced by various multimedia content – graphics, video and audio - which complement the product. It should offer focused content that justifies its existence as a separate website.
Minisites are often temporary and are removed from Web once the promotion is over or the information is no longer relevant.
Creating minisites can be a good strategy for increasing Web traffic to a parent website and therefore more sales. They are very high converting, and many types of businesses choose to utilise them for their marketing campaigns for that reason.

Any kind of company can benefit from a minisite in the form of a landing page.