Merge sort is a popular sorting algorithm that follows the divide-and-conquer approach. It works by dividing an unsorted list into smaller sublists until each sublist contains a single element. These individual elements are then merged back together in a sorted order. The merging process involves comparing the elements of the sublists and combining them into a new sorted list. This continues until all sublists are merged into one fully sorted list. Merge sort is efficient for large datasets and has a time complexity of O(n log n), making it a reliable choice for sorting tasks.