A binary search tree (BST) is a data structure that organizes data in a hierarchical manner. Each node in a BST contains a value, and it has at most two children: a left child and a right child. The left child's value is always less than its parent's value, while the right child's value is greater. This property allows for efficient searching, insertion, and deletion of values. In a BST, operations like searching for a value can be performed quickly, typically in O(log n) time, where n is the number of nodes. This efficiency makes binary search trees useful for applications that require sorted data and quick access, such as databases and memory management systems.