I can't visualize anything in my head. I've never been able to. I think in words as a second language of sorts. My default is to think in concepts and ideas. I then try to translate that to words if I need or want to express those ideas outside of my own head.
For me, thinking in words is like, say I want to think about what my oldest daughter looks like. I can't see an actual image of her in my mind. I can, however, use words to put together an idea of what she looks like if I felt the need to explain it to someone. Example, she has brown hair that is currently dyed red. She has solid brown eyes close to the color of coffee. Her complexion is a light shade of tan with an olive hue to it. I don't see the red, the brown, or the olive, but it's a point of reference that provides a verbal image that I know is accurate and would make sense to anyone listening to me.
Yeah, that's a general idea of what thinking in words v/s images is for me. Even though I cannot see an image, I can use words to describe the image from things I remember/know.