Creates a group in a select input field. When a lot of options area available, it is convenient to group options by category. Each option element is places within the optgroup tags. The label attribute will be the option category text.
<optgroup attributes> ... </optgorup>
<select>
<optgroup value=”Category 1”>
<option value=”one”>Option in first category</option>
</optgorup>
<optgroup value=”Category 2”>
<option value=”two”>Option in second category</option>
</optgorup>
</select>