Accessibility refers to how software or hardware combinations are designed to make a system accessible to persons with disabilities, such as visual impairment, hearing loss, or limited dexterity.
For example, a website developed with accessibility in mind might have text-to-speech capabilities. In the USA public websites have to have accessible compliance. It’s defined in 508 compliance. It gives the guidelines and best practices for all website users that should be met with key areas of accessibility.