The <li> tag in HTML is used to define a list item. It is most commonly used inside list containers like <ul> (unordered list) and <ol> (ordered list), and sometimes <menu> (for a list of commands or options). Each <li> represents a single item within these lists.

Usage:

1. Unordered List (<ul>): Items are usually presented with bullet points.
2. Ordered List (<ol>): Items are presented in a numbered sequence.

Example with an Unordered List:

<ul>
  <li>Apples</li>
  <li>Bananas</li>
  <li>Cherries</li>
</ul>

This will display as:

• Apples
• Bananas
• Cherries

Example with an Ordered List:

<ol>
  <li>First Step</li>
  <li>Second Step</li>
  <li>Third Step</li>
</ol>

This will display as:

1. First Step
2. Second Step
3. Third Step

Key Points:

• Unordered List (<ul>): The <li> items are displayed with bullet points, but the bullets can be styled or removed using CSS.
• Ordered List (<ol>): The <li> items are displayed with numbers or letters, and the numbering format can be customized with the type attribute (e.g., <ol type="A"> for uppercase letters).
• Nesting: Lists can be nested, meaning you can have lists within lists (both ordered and unordered).

Example of a Nested List:

<ul>
  <li>Fruits
    <ul>
      <li>Apples</li>
      <li>Bananas</li>
    </ul>
  </li>
  <li>Vegetables</li>
</ul>

This would look like:

• Fruits
  • Apples
  • Bananas
• Vegetables

The <li> tag is essential for creating structured lists in HTML, making content more organized and readable.