An example comes from a cartoon where there is a woman talking to her boyfriend.
There's a "cloud" that comes from her mouth, and the text inside reads: "You're so handsome." But there is another cloud that comes from the top of her head (brain), and the text reads: "Man, does he have bad breath."
What are these "clouds" called? Would "halo" be a suitable term?
And what is this technique called that shows what a character is really thinking as opposed to what she is saying?