Web Accessibility is the practice of making the website easy to use for individuals with disabilities or impairments.
Those with the following impairments will benefit from Web Accessibility:
Visual impairment - includes blindness, near-sightedness, color blindness, etc.
Hearing impairment - including deaf users, those who are hard of hearing, etc.
Physical or mobility impairment - including those with muscle disorders, loss of limbs, etc.
Cognitive impairment - Learning disabilities, Developmental disabilities, Intellectual disabilities, certain neurological conditions, etc.
A combination of any of the above, and/or other impairments
Web Accessibility incorporates standards, tools, best practices, and technologies to allow these individuals access to the Web in meaningful ways.
Screen Reading tools for low vision
WCAG - International standards for Web Content Creators
Authoring Tools (tools used to create web pages: CMS, LMS, Blog software, and other software or content processing/conversion tools)
International and Developer communities and conferences to discuss and update standards