This test will assess the accessibility of a website, ensuring that it is usable for all users regardless of their abilities or disabilities. This includes testing for compatibility with assistive technologies, such as screen readers, as well as ensuring that the site is navigable with a keyboard or other input device.
From Wikipedia
Accessibility is the design of products, devices, services, vehicles, or environments to be usable by disabled people. The concept of accessible design and practice of accessible developments ensures both "direct access" and "indirect access" meaning compatibility with a person's assistive technology.