It is the degree to which a product, environment or service is designed to be available to as many people as possible.
There are different dimensions to accessibility, the most common ones being physical, technological, and attitudinal.
a) Physical Accessibility caters to those with walkers, wheelchairs, canes, etc. The location of your workplace needs to be physically accessible to as many people as possible, by making structural decisions such as the construction of ramps, elevators, open/wide pathways, etc.
b) Technological Accessibility refers to the company websites and other softwares being designed and maintained in a manner that people with disabilities (such as visual and hearing impaired people) can access them.
c) Attitudinal Accessibility refers to making your workforce aware about the challenges faced by people with disabilities, and taking measures to remove any attitudinal barriers and misconceptions that may hamper their experience at work.
Making your workplace diverse and inclusive involves improving accessibility on various fronts. The most common way would be to incorporate an infrastructure that can accommodate the needs of as many people as possible, despite varying requirements (such as physical/emotional/mental challenges).