Description:

The <optgroup> tag is used for grouping related options within your select list. This makes it easier for users to comprehend their choices when looking at a large list.

Example Code:
<select>
  <optgroup label="Fruits">
    <option value="banana">Banana</option>
    <option value="orange">Orange</option>
    <option value="apple">Apple</option>
  </optgroup>
  <optgroup label="Vegetables">
    <option value="carrot">Carrot</option>
    <option value="tomato">Tomato</option>
    <option value="onion">Onion</option>
  </optgroup>
</select>
Result:
Attributes:
Attribute Definition
label Specifies a label for the option group.
disabled Disables the input control. The button won't accept changes from the user. It also cannot receive focus and will be skipped when tabbing.
Global Attributes:

The <optgroup> tag also supports the Global Attributes in HTML5

Event Attributes:

The <optgroup> tag also supports the Event Attributes in HTML5