So I have aphantasia, and I first realized when talking to someone about mental images and memories. They have photorealistic pictures in their mind, or even video scenes like a movie. At my best I have something like an expressionist painting with words and concepts arranged spatially on blobs of color representing the object. More typically, just blackness.

Here is another description of it, and a test in the first part: https://www.youtube.com/watch?v=ewsGmhAjjjI