Auto-focus is a feature in cameras that automatically adjusts the lens to ensure that the subject is sharp and clear in the image. This technology uses sensors to detect contrast and distance, allowing the camera to focus on the desired subject without manual intervention. There are different types of auto-focus systems, including phase detection and contrast detection. Phase detection is typically faster and is commonly found in DSLR cameras, while contrast detection is often used in mirrorless cameras and smartphones. Both methods aim to enhance the photography experience by simplifying the focusing process.