Visualising is understanding the texts by creating an image in our mind of whats happening in the text.
Visualising is to help people understand the text by creating an image brain. For an example: If a person was in a exceptional boredom then saw a frog pressed in the window nearest to that person and looking at him. The image would be like a person and a frog staring at each other.
Visualising helps people create mental images in their head.