What Is Purpose Of Getdescendant Method In The Following Codep #186

What is purpose of GetDescendant method in the following code?</p> <pre><code class="language-sql">DECLARE @parent HierarchyId = HierarchyId::GetRoot() INSERT INTO H (Node,ID,Name) VALUES (@parent.GetDescendant(NULL,NULL),2,'Johnny') </code></pre>

This multiple choice question (MCQ) is related to the book/course gs gs116 Microsoft SQL Server. It can also be found in gs gs116 SQL Server Beyond Relational - Hierarchies - Quiz No.1.

DECLARE @parent HierarchyId = HierarchyId::GetRoot() INSERT INTO H (Node,ID,Name) VALUES (@parent.GetDescendant(NULL,NULL),2,'Johnny')