You can use this feature to "diff" the contents of two directories that are supposed to the same. All information is provided on a report, such as different file sizes, date stamps, extra files, missing files, etc. I use this feature to check a staging directory before making a CD.
To quickly set a directory bookmark, hold down CTRL as you click the right or left icon.
To go to a bookmarked directory, click the right or left icon. You can also use the CTRL-F1 or CTRL-F2 hotkeys.