The dialog box conveys what characters are saying and it’s a UI element the player is going to see over and over again. That’s why its’ design needs special attention.
An icon is an image or symbol that represents a concept and, inside JRPG video game, these are very aware inside the main menu.
I recently finished one called “I am Setsuna”. I decided to play it when I read about how it was inspired in “Chrono Trigger”, one of the best games I ever played.