Option group. Defines a group of option elements in a select form field.
The HTML <optgroup> tag is used for grouping related options within your select list. This makes it easier for users to comprehend the options when looking at a large list.
<select name="furniture"> <optgroup label="Kitchen"> <option>Chair</option> <option>Table</option> </optgroup> <optgroup label="Living"> <option>Sofa</option> <option>TV</option> </optgroup> </select>