Uppercase will convert all highlighted text to UPPERCASE
Lowercase will convert all highlighted text to lowercase
Title case will capitalize the first letter of each work in the highlighted text
Until now, users had to download and install a Google Doc add-on called Change Case. Note the Change Case add-on offers more options than the GSFE update. One option that I really like is the Sentence Case option which will capitalize the first letter of the sentence as opposed to Title Case, where the first letter of every word is capitalized.
For either option, I would recommend highlighting the text first, then use the new feature to change the case of the text.
Below is a short animation on using this new feature.