Usability is the measure of a product's potential to accomplish the goals of the user. In information technology, the term is often used in relation to software applications and Web sites, but it can be used in relation to any product that is employed to accomplish a task (for example, a toaster, a car dashboard, or an alarm clock). Some factors used in determining product usability are ease-of-use, visual consistency, and a clear, defined process for evolution.
Usability testing is a method by which users of a product are asked to perform certain tasks in an effort to measure the product's ease-of-use, task time, and the user's perception of the experience. Usability testing can be done formally, in a usability lab with video cameras, or informally, with paper mock-ups of an application or Web site. Changes are made to the application or site based on the findings of the usability tests. Whether the test is formal or informal, usability test participants are encouraged to think aloud and voice their every opinion. Usability testing is best used in conjunction with user-centered design, a method by which a product is designed according to the needs and specifications of users.
Within the last several years, the usability of Web sites has become a hot topic for Web developers. Many major Web sites employ usability engineers to ensure that they have an easy-to-use, friendly site that provides a positive customer experience. Major sites such as Drugstore.com and Altavista.com have recently been re-designed based on recommendations made during usability tests and evaluations.