Below is a video on how to use all of the icons on the Review Ribbon. If you scroll down below the video, you can get clickable quick access to each of the icon explanations in the video shown below.

0:00 Review Ribbon Icons

0:05 Spell Check

0:09 Workbook Statistics

0:20 Check Accessibility

0:31 Smart Lookup

0:45 Translate

0:46 Show Changes

1:05 Show All Comments

1:08 Notes

1:20 Password Protection