The rightmost three columns are the ratios of the three sorts to each other. Reasons for this are discussed below in the Efficiency section. The results for real arrays are summarized in Table 2. This table is laid out the same as the one above. Bubble sort gets there by doing N comparisons each time it goes through the array, which it does N times.
Insertion sort does things the opposite way.
The most obvious advantage that Insertion sort has over both Selection and Bubble sorts is the fact that no swapping takes place in Insertion sort. So we can see why Selection sort and Insertion sort are both faster than Bubble sort, but not why Insertion sort is faster than Selection sort. There are two possibilities. One is that the swap used in Selection sort is a function call, and thus is slowing it down. However, if you remove the function call and build the swapping directly into the algorithm, performance does not increase significantly.