What are the key differences between a heap and a binary search tree (BST)?

A heap is a complete binary tree where each node has a value greater than or equal to its children (max heap) or less than or equal to its children (min heap). A binary search tree is a binary tree where the left child of a node has a value less than the node and the right child has a value greater than the node. The key difference is that a heap does not have a specific order between parent and child nodes, while a binary search tree maintains a specific order for efficient searching.