1.3.1 Info and Relationships
Create content that can be presented in different ways ( for example simpler layout ) without losing information or structure.

About

While normal users can view the layout of a webpage and quickly understand it’s hierarchy and structure; people with visual impairments cannot see this layout. The website needs to be provided with an appropriate markup to illustrate its structure to screen readers in order to be accessible to persons with visual impairments. The links should be categorized into various groups to enable screen readers to determine their relationship.

Example:

Before Rectification

Content image without titles.

With video as this one; people with visually difficulties will be able to hear the audio but will not be able to see the picture.

After Rectification

Content image with titles.