Market segmentation involves dividing a market into subgroups of consumers with distinct needs and behaviors. It allows companies to target specific segments and position their products to appeal to certain groups. The key aspects of segmentation are identifying subsets of buyers with similar needs, evaluating segments based on criteria like viability and accessibility, and segmenting markets in different ways such as by geography, demographics, or lifestyle. After segmentation, companies select target segments and develop positioning strategies to distinguish their products from competitors within the targeted segments.