The document discusses several sorting algorithms:
1. Shell sort improves on insertion sort by sorting elements farther apart before closer elements.
2. Bubble sort compares adjacent elements and swaps them if out of order, repeating until sorted.
3. Quicksort chooses a "pivot" element and partitions the array into subarrays of smaller and larger elements, recursively sorting them.
4. Selection sort finds the minimum element and swaps it into the sorted portion of the array.