In this video, the teacher explains the importance of using concrete details in writing to help readers visualize a text. They provide examples and guide the viewers through an exercise to identify and rewrite sentences with abstract details into ones with concrete details. The teacher emphasizes that concrete details create vivid images in the reader's mind and make the writing more descriptive and interesting. The viewers are then encouraged to apply what they've learned to revise their own writing and create images for their readers using specific, concrete descriptions.