Explain what a Binary Search Tree is.

A Binary Search Tree (BST) is a special type of binary tree that is used to store data in an organized fashion. It has the following properties:

1. Each node contains a single key value.

2. The key values of all the nodes in the left subtree are smaller than or equal to the key value of the parent node.

3. The key values of all the nodes in the right subtree are larger than or equal to the key value of the parent node.

4. Both the left and right subtrees must also be binary search trees.

Binary Search Trees provide an efficient way of organizing and searching for data. They are used in many applications, such as databases and search engines.