Abstract vs concrete is not the main difference of images vs text.

The main difference is that an image (without text in it) can relay a lot of information at once. Counter example: try reproducing an image from a description.

A text on the other hand is able to give unambiguous explanation of relationships. Counter example: try painting “a primary and a secondary disk” as an image without any text.

So images are good to give an overview fast, but text is needed to make it unambiguous.