The phrase "что он рисует?" is translated as "what is he drawing?". I'm interested in why not 'paint'? It seems to me that to paint and to draw is kind of the same in Russian? If we open a random website about art and craft in English we can see even two different categories for painting and for drawing: https://diysguide.com/category/painting/. And we understand the difference. Are there any other words except рисовать? (sorry, it's not my native)
In English, the word painting represents creating art impressions using wet media (like paint, pigment, dye), while drawing encompasses dry media (graphite, chalk) as well as wet media/shaped tip (pen, marker) impressions.
In Russian, there is no such distinction. There is only one generic word for creating artistic impressions by hand - "рисовать". Other words that might be used as synonyms ("изображать", "раскрашивать", "писать" etc.) can be used only in narrow contexts.
There are some words in Russian to designate various types of making images:
рисовать (from рисунок — a picture) — to paint, to make an illustration, a picture;
чертить (from черта — a line) — to make technical drawings;
изображать (from изображение — an image) — to make an image; also could be use as a synonym for imitate;
красить, раскрашивать (from краска — dye) — to fill (a contour), to paint smth with dye, color pencils, markers, etc.;
иллюстрировать (from иллюстрация — an illustration) — to illustrate;
писать (lit. to write) (jarg.) — to paint a picture (using by painters).
Of course, there could be used a lot of prefixes, especially for рисовать: нарисовать, разрисовать, отрисовать, обрисовать.
Meaning of the question "Что он рисует?" depends on context. If you are talking about a kid, it may mean "drawing"o or "painting". But if you are talking about a professional artist, it means "What is he drawing?" only. If an artist is using oil paint, the question would be "Что он пишет?" or "Над чем он сечас работает?". It would be illiterate to say about a painter "Он рисует". This is a part of a professional jargon, I think. I know, because I used to speak with artists in Russia.