In addition to the general meaning that Jonathan pointed out, accessible may also have meanings related to people with disabilities. An accessible source will be available in different forms for people that are blind, deaf, or otherwise have a disability that would prevent them from reading/watching/listening to a source of information. Such as text-to-speech, braille, larger font, etc. It is a common area of development in high education; there are various legal requirements that must be met in order to prevent the institution from legal issues. Often, sources must be accessible, for example, for all students that may attend the university.

It's easy to read and easy to understand. There aren't a lot of difficult words or complex topics.