Responsive images allow web pages to load the most optimally sized image for different devices by using new HTML elements like <picture> and attributes like srcset. This improves page load performance by reducing image file sizes since the largest possible image is no longer sent to all devices. Images currently make up over 63% of average web page sizes so responsive images are important for performance. <picture> allows selecting different image sources for different screen sizes or device capabilities while srcset specifies multiple image resolutions for a browser to choose from to match a device's resolution.