Can anyone explain me the purpose of this line in splay tree function in c++

Question

splay* Insert(int key, splay* root)
{
static splay* p_node = NULL;
if (!p_node)
p_node = New_Node(key);
else
p_node->key = key;
if (!root)
{
root = p_node;
p_node = NULL;
//return root;
}
root = Splay(key, root);
/* This is BST that, all keys <= root->key is in root->lchild, all keys >
root->key is in root->rchild. */
if (key < root->key)
{
p_node->lchild = root->lchild;
p_node->rchild = root;
root->lchild = NULL;
root = p_node;
}
else if (key > root->key)
{
//explain the line just below thus comment
p_node->rchild = root->rchild;
p_node->lchild = root;
root->rchild = NULL;
root = p_node;
}
else
return root;
p_node = NULL;
return root;
}

Answer 1

I think that the meaning is

If root's key is smaller, make root as left child
of newnode and copy the right child of root to newnode

Answer 2

Read this article and try the implementation in playground to understand better...
https://www.geeksforgeeks.org/splay-tree-set-2-insert-delete/