The document discusses cohesive devices, which are linguistic elements like transitional words and paragraph hooks that show logical relationships between parts of an essay. Cohesive devices help achieve coherence by linking sentences and paragraphs together smoothly to carry thoughts from one idea to the next without abrupt jumps. They signal relationships among parts to help readers accurately follow the writer's train of thought. There are different types of cohesive devices that lead readers to make connections or draw conclusions in various ways.