Verbal thinking is talking to yourself silently, and visual thinking is seeing things in your imagination. A verbal thinker is someone who thinks primarily in the first way and a visual thinker is someone who thinks primarily in the second way.

There was a debate, in the late 1800s, about whether "imagination" was simply a turn of phrase or a real phenomenon. That is, can people actually create images in their minds which they see vividly, or do they simply say "I saw it in my mind" as a metaphor for considering what it looked like?

[... Francis] Galton gave people some very detailed surveys, and found that some people did have mental imagery and others didn't.

-- Yvain, "Generalizing from One Example"

When I was a kid growing up in Far Rockaway, I had a friend named Bernie Walker. We both had "labs" at home, and we would do various "experiments." One time, we were discussing something -- we must have been eleven or twelve at the time -- and I said, "But thinking is nothing but talking to yourself inside."

"How yeah?" Bernie said. "Do you know the crazy shape of the crankshaft in a car?"

"Yeah, what of it?"

"Good. Now, tell me: how did you describe it when you were talking to yourself?"

-- Richard Feynman, What Do You Care What Other People Think?