What aspect of accessibility is covered by the 'Keyboard Accessibility' guideline?

The guideline for 'Keyboard Accessibility' primarily focuses on ensuring that all users, particularly those with mobility impairments, can navigate and interact with digital content using a keyboard alone, rather than requiring a mouse or other pointing device. This aspect of accessibility is crucial because many individuals with certain disabilities may have difficulty using a mouse due to limited motor skills or dexterity.

By adhering to keyboard accessibility guidelines, designers and developers can create interfaces that allow for full user engagement through keyboard navigation. This not only benefits those with disabilities but also enhances usability for all users under various situations, such as those using mobile devices or desktop setups without a mouse.

While other options might address aspects of accessibility indirectly related to users' experiences, they do not specifically address the unique concerns of individuals who rely on keyboard functions for interaction, which is the central focus of the guideline in question.