Comparing and contrasting activities require students to make connections between their own knowledge and the text and/or between the different concepts explored within a text, leading to a deeper understanding of the content. These type of activities also require students to identify key vocabulary which subsequently assists in vocabulary development. Graphic organisers such as Venn diagrams are a particularly useful way to help students compare and contrast information.
Dreher, M., & Gray, J. (2009). Compare, Contrast, Comprehend: Using Compare-Contrast Text Structures With ELLs in K-3 Classrooms. The Reading Teacher, 63(2), 132-141.