It is a lack of visual or sensory imagery, but not a lack of imagination.

It really depends on how you define aphantasia. Often the VVIQ score is used, a vividness score ranging from 16 to 80.

About 0,8 % of people have a score of 16, and 3,9 % have a score <= 32. The figures are from one of the more recent studies. Other studies report similar figures, for example one study by Zeman found 0,7 % with a score of 16.

About ¼ of all people with visual aphantasia also have multisensory aphantasia (all classical senses and emotions).

As an aphantasic, I remember what I know about the Mona Lisa. I know that her lips are famous, I think her face is placed more to the right, and her hair and clothes are dark. I am not sure if you can see her hands, I would have said you cannot (I checked and I am wrong).

Apparently, I was never aware enough of her hands to know that they were in the painting. And I could not tell you how her hair lies or what her smile looks like.

It is not word-based, but just knowing. I just know the clothes are dark. There is no experience that can be edited.

When I collect the characteristics to write them down, I think in words.