Dynamic layouts are designs that adapt to different screen sizes and orientations, ensuring a consistent user experience across devices. They automatically rearrange content based on the available space, making websites and applications more responsive and user-friendly. This adaptability is crucial for modern web design, as users access content from various devices, including smartphones, tablets, and desktops. Using techniques like CSS Grid and Flexbox, developers can create flexible layouts that respond to changes in the viewport. Dynamic layouts enhance usability by prioritizing important information and maintaining visual appeal, ultimately improving user engagement and satisfaction.