What needs to be pressed when word automatically corrects misspelled words and displays the corrected word?

You don't need to press anything! When Word automatically corrects a misspelled word, it simply replaces the incorrect word with the corrected one.

However, if you want to undo the automatic correction, you can press:

* Ctrl + Z (Windows) or Command + Z (Mac) to undo the last action, which in this case would be the automatic correction.