title: what is exact difference between appbar, toolbar, actionbar ? and when to use them specifically?
body: <p>what is exact difference between <code>appbar</code>, <code>Toolbar</code>, <code>Actionbar</code>? and when to use them specifically?
  I try to find about them but it make me confuse so can any buddy explain to me what is exact difference between them and when to use them or are this are the same name of the single component?</p>