Key Features:

Flexible Grids: Websites are built with grids that can dynamically adjust to different screen sizes, allowing content to rearrange and maintain readability. 
Responsive Images: Images scale proportionally to fit the screen, preventing distortion or excessive scrolling. 
Fluid Layouts: Elements resize appropriately, enabling the website to adapt to the user's screen size. 
Adaptive Images: Images are sized using relative units to ensure they adapt to the available screen space without losing quality or creating layout issues. 

Benefits:

Improved User Experience: Users have a consistent and optimal experience across all devices. 
Enhanced SEO: Mobile-friendly websites are favored by search engines, leading to better rankings. 
Cost-Effective: One website design can serve all devices, reducing development and maintenance costs. 
Increased Reach: A wider audience can access the website, regardless of their device. 
Easier Maintenance: A single codebase is easier to update and maintain than multiple designs. 
Faster Loading Time: Optimized images and code contribute to faster loading speeds, improving user experience. 
Competitive Advantage: A responsive website demonstrates a commitment to user experience and modern web practices.