The document discusses heaps and heapsort. It defines max heaps and min heaps as complete binary trees where each node's key value is greater than or less than its children's key values, respectively. It describes operations on heaps like insertion, deletion of the max/min element, and creation of an empty heap. Algorithms for insertion and deletion into max heaps are provided, with examples. Heapsort is described as using insertion to build a max heap of the input array and then deleting elements to sort the array.