Weighted Sort sorts percentage columns of data in order of importance instead of simply numerical order. For example, if you sort by Bounce Rate in descending order, the rows with 100% bounce rate will appear first, even if these bounce rates are based on only one or two sessions. However, by applying Weighted, you bring those rows with the highest and statistically most significant bounce rates to the top of the list.
To use Weighted Sort, click the Bounce Rate (or other percentage based metric) column header in a table. This will sort the rows in the table. Then, above the table, use the Sort Type selection menu to select Weighted.