<optgroup> tag in HTML
The <optgroup> tag represents a defined group of options , that belongs to a <select> tag.
The <optgroup> tag groups the related items in an drop down list.
label attribute in <optgroup> tag
The label attribute is required in this tag and should provide users with a hint or description about the contents of the group.
disabled attribute in <optgroup> tag
This attribute is used to disable a complete group of options at once.
This will ban the user from interacting with all options in the disabled group.