Detailed answer
Aside is for content tangentially related to its surroundings, such as related reading.
Being visually positioned on the side does not automatically make something an aside. Essential instructions belong in the main flow even if a design displays them in a narrow column. Choose structure before applying layout.
Example
<aside aria-labelledby="related"><h2 id="related">Related reading</h2><a href="/forms/">HTML forms</a></aside>
Understanding the behavior
An aside contains complementary material that is related but separable from the surrounding content. Visual placement on the right does not establish that relationship. Essential instructions should stay in the main reading flow even when the design resembles a sidebar.
Practical implementation notes
Check the page on a narrow screen where the columns stack. The content order should remain sensible, and the aside should not interrupt the middle of a sentence or a required form task.
How to check it
Remove the panel temporarily and reread the main article from beginning to end.
Expected result
The main explanation still makes sense without the aside.
Watch out: Do not move essential article steps outside its main content for visual reasons.
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