When an electronic resource is "accessible", it can be accessed by an individual with a disability and does not require any particular sense such as vision, hearing, or fine motor manipulation, to perform any of the core functions, or perceive information as the author intended.
In other words, when a webpage, document, video, software application, or hardware control panel is "accessible," any user will be able to interact with or understand information as presented. Accessibility, as a field, considers that access by a variety of individuals with disabilities will occur. Those individuals may be using a variety of facilitated access while consuming information or interacting with a specific resource.
Facilitated access to Information and Communication Technologies occurs for an individual with a disability through the use of assistive technologies, such as screen readers, on-screen magnification, alternate input devices, etc.
Accessibility is purposeful, and as such, requires that the author or developer implement techniques early in the content creation or development process. To learn how important accessibility is to a variety of individuals with disabilities, navigate to the W3C Perspectives Videos on the main menu.