What are hints in hintboxes
Every time you press the Ctrl key, a couple of semi-transparent hintboxes appear on the screen. These are hints.
They have a very useful purpose, because they tell you which hotkey you can press to quickly open pre-defined folders, convert metric/imperial units or paste strings stored in the clipboard manager.
Explanations of the individual rows
1st row: hotkeys to quickly open pre-defined folders.
2nd row: hotkeys to convert metric/imperial units
3rd/4th row: this is the clipboard manager; press the pre-defined hotkeys to quickly insert strings stored in memory into your target application (a CAT tool, a text processing application, etc.)
How to toggle the hintboxes on/off
If you do not wish the hintboxes to be shown every time you press the Ctrl key, press Ctrl+Alt+H to toggle the hint boxes off or back on.
You can also uncheck the “Show hints” checkbox on the “Language & Settings” tab.
You might want to watch this video as well: