What does `:_*` (colon underscore star) do in Scala?

I have the following piece of code from this question: def addChild(n: Node, newChild: Node) = n match { case Elem(prefix, label, attribs, scope, child @ _*) => Elem(prefix, label, attribs, scope, child ++ newChild : _*) case _ => error("Can only add children to elements!") } Everything in it is pretty clear, except this piece: child ++ newChild : _* What does it do? I understand there is Seq[Node