This means users can identify elements of the interface and content through the use of their senses. For many users, this means visually, but for others it can also be through touch or sound.
This means the user can interact with site elements such as buttons and navigation. For some users this means seeing an element and then tapping or clicking on the control. Other users may rely on voice commands or keyboard-only controls.
When technology is understandable, it follows predictable patterns and is consistent in its design patterns. This is arguably the element that reduces access for the most broad set of users, regardless of any impairments.
Robust websites are designed to operate across all appropriate technologies. Again, this is an element of accessibility that can help