A light shine is drawn on the front face of each letter, inset by the margin and sized and rounded by the controls. It follows the letter outline rather than sitting as a separate offset copy, so it reads as a reflection on the face.
Highlight is applied as an Illustrator live effect, so the text stays editable. Change the word, the font, or any slider afterwards, and save the result as a Graphic Style to reuse it.
How to add a shine to text in Illustrator → walks through the manual Illustrator steps, then shows the one-click version.