Text bubbles normally contain a description of the action, the back story or dialog, but that is not all that they can contain or do. Sometimes the authors take special care to integrate the text into the art so that the graphical narrative and the textual can work alongside one another rather than compete for the reader’s attention. One version of this can be seen in the webcomic Romantically Apocalyptic. Wherein most of the text is kept within the borders between the panels, usually this is used for the narrator’s voice and other sound effects still happen inside the panel but without bubbles or boxes to contain the words.
Another use of text bubbles is for words, or languages, that are fictional, words that have not, or can not, be spoken by human beings. A great example of this can be seen in Rice Boy by Evan Dahm. In it the titular Rice Boy meets a race whose tongue he doesn’t understand, rather than use words the language is represented as symbols. Even after Rice Boy learns to “speak” the language it is never translated for the reader. This is a case where the Text bubbles do exactly what they are supposed to be doing but the reader must make use of context clues to make sense of the story. Just like the character does, which allows the reader to engage the story on the same level as the character.
Another usage of text bubbles is the graphical text bubble. In Dresden Codak there is a short story comic that talks in detail about how odd the working of human memory are. One of the ways a poorly remembered memory is conveyed in by groups of small text bubbles that contain pictures. For a couple of panels that have no words the idea of there being a number of thoughts associated with the puppet is clearly conveyed.