Not understand borh functions insert and print

#1

how recursion works in the insert function and return root?

#2 
node*buildTree(){
	int d;
	cin>>d;
	if(d==-1){
		return null;
	}
	root=new node(d);
	root->left=buildTree(root->left);
	root->right=buildTree(root->right);
	return root;
}

first we take input d and make its node
then we construct it’s left subtree
then we construct it’s right subtree
now return the root node

this will work for each node and build the tree

for detailed explanation watch the video again

#3

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