What is the purpose of the aside tag in HTML?

The purpose of the aside tag in HTML is to provide content that is tangentially related to the main content of a document, often functioning as a side note or a side story. This can include information like quotes, related links, or even advertisements that complement the main article but are not essential to its primary message.

Using the aside tag correctly helps to enhance the semantic structure of your HTML, allowing users and search engines to understand that this content is not a core part of the main narrative but still relevant in a supplementary way. It is distinct from content that is central to the understanding of the main topic and serves to provide additional yet non-essential information, which is why marking off a side story is the most appropriate description of the aside tag's function in HTML.