You can convey an item's relative level of importance based on its placement in relation to other things on your page. More important items/actions should be placed at the top or bottom of the screen. Related items of a similar hierarchy should be placed next to each other.

Creating a Hierarchy of Importance

When designing an app, each button, image, and line of test increases the complexity of your UI design.

You can simplify how your UI is understood by using the following:
- Clear visible elements
- Sufficient contrast and size
- Key information is distinguishable at a glance 
- A clear hierarchy of importance

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Organizing your information in a way that's intuitive helps users easily navigate through your app and help determine what's important. Information can be emphasized through things like color, shape, text, and motion to add clarity.

Information Hierarchy

Material Design Documentation

Simplifying Your UI with a Hierarchy

Since screen readers rely on the top-down structure of HTML, in order to ensure that screen readers are able to read content out loud in the intended hierarchical order, designers need to collaborate with developers to both write out the HTML in the correct order as well as understanding how screen readers interpret information. 

Visual Hierarchy and Screen Readers

Focus order is the order in which your user focuses on different items on your screen. Focus order can follow either the order of the visual layout(usually from top to bottom of the screen) or from most important to least important item. Focus points can be expressed through a combination of visual indicators and accessibility text.

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