A Binary Search Tree (BST) is a type of tree data structure where each node can have up to two children, known as the left child and right child. In a BST, all nodes located to the left of a node x are less than or equal to x, while all nodes to the right of x are greater than x. When adding a new node to a BST, we begin at the root node. The new node is navigated down the tree, moving left if it is less than the current node and right if it is greater. If the child in the direction we want to go is null, we insert the new node in that position. For instance, to insert 15 into the following BST: 10 / \ 5 20 / \ 4 7 We start at the root (10), and since 15 is greater than 10, we proceed to the right. Now at 20, we see that 15 is less than 20, so we move to the left. As the left side of 20 is empty, we insert the new node 15 there. The updated BST will look like this: 10 / \ 5 20 / \ / 4 7 15