A browsing context name is a non-empty string which does not begin with _ (an underscore), and may be specified as the value of name attributes for iframe, object, and frame elements. Browsing context keywords, i.e. one of _self (the default), _blank, _parent, or _top, indicate browsing contexts relative to the current document.[1] Scripts and values of target attributes for a and form elements may indicate browsing contexts by either names or keywords.
_selfcontains an element or script._parentcontains the element (such asobject,iframe, orframe) in which_selfis embedded, or_selfif it is not embedded._topis not embedded within any other and contains, directly or indirectly, an element or script. This may be equal to either_selfor_parent, or an ancestor of both._blankdoes not yet exist, but will be created if a script or element operated by the user sends a URL to it. (A name which is not yet assigned to a browsing context has a similar effect, except the resulting context has a name by which it may be referred to later.)