The <aside> element in HTML5 is used to define content that is tangentially related to the content around it. It is typically used for sidebars, pull quotes, or information that is considered supplementary to the main content of the page.

Syntax:

<aside>
      <h1>Contents...</h1>
      <p>Contents...</p>
</aside>

Features:

• Supplementary Content: <aside> is used for content that is related to the main content but is considered secondary or supplementary.
• Sidebars: Often used for sidebars containing additional information, links, or advertisements.
• Accessibility: Helps improve the structure and accessibility of the document, making it clear what content is supplementary.