In a min-heap stored in a slice, the children of index i are 2i+1 and 2i+2, and the parent is (i-1)/2. Push appends and sifts up; Pop moves the last item to the root and sifts down. Both are O(log n), Peek is O(1). Siblings are not ordered, so a heap is not a sorted list.
Binary heap
A complete binary tree stored in a slice where every parent is not larger than its children; the minimum is always at index 0.