The Sobel operator is a popular image processing technique used to detect edges in images. It works by calculating the gradient of the image intensity at each pixel, highlighting areas where there is a significant change in brightness. This helps in identifying the boundaries of objects within an image. The Sobel operator uses two 3x3 convolution kernels, one for detecting horizontal edges and another for vertical edges. By applying these kernels to an image, it produces two gradient images that can be combined to find the overall edge strength and direction, making it useful in various applications like computer vision and machine learning.