What is the Node class of a Binary Search Tree?
The Node class is a class with two fields and the usual getter and setter methods.
int key an unique key to identify this Node
E data stores a single element of the list
Node<E> left point to the left branch
Node<E> right point to the right branch
What is the BST class?
The BST class is a class with one field and the usual constructors and methods.
Node<E> root point to the very top Node of the BST. If the BST is empty, then the head is null.
Reading
Binary Search Trees (Princeton University) - https://algs4.cs.princeton.edu/32bst/