Bicubic interpolation is a mathematical method used to estimate pixel values in digital images. It works by considering the closest 16 pixels (a 4x4 grid) around the target pixel and uses cubic polynomials to calculate a smooth transition between them. This results in higher-quality images compared to simpler methods like bilinear interpolation. This technique is particularly useful in image resizing, where it helps maintain sharpness and detail. By analyzing the surrounding pixels, bicubic interpolation can create new pixel values that blend well, making the resized image look more natural and visually appealing.