The tag.

Tag names are structured as CATEGORY::TAG_NAME, with a :: separating the category and tag name. Category names will be returned with :: in their name.

Example: Skills:: would indicate a category named skills. Further, Skills::ActionScript would indicate a tag named ActionScript within the Skills category.

New category and tag names may not start or end with whitespace, so creating Skills:: ActionScript is rejected. Whitespace within a name is allowed: Front End::Dust Bringer is valid.