Quick sort is a popular sorting algorithm that uses a divide-and-conquer approach to arrange elements in a list. It works by selecting a pivot element from the array and partitioning the other elements into two sub-arrays: those less than the pivot and those greater than the pivot. This process is repeated recursively for the sub-arrays until the entire list is sorted. The efficiency of quick sort comes from its average-case time complexity of O(n log n), making it faster than many other sorting algorithms for large datasets. However, its worst-case time complexity is O(n²), which can occur when the smallest or largest element is consistently chosen as the pivot.