In OpenCV, Gaussian Blur is a smoothing filter that is used to reduce noise and other small details in an image. The filter is based on the Gaussian function, which is a bell-shaped curve that tapers off as the distance from the center increases. The cv2.GaussianBlur() function is used to apply a Gaussian blur to an image.

The function takes in three required parameters: the image to be blurred, the size of the kernel (specified as a tuple of width and height), and the standard deviation in the x and y direction (specified as a tuple of width and height). The kernel size determines the size of the area used to calculate the blur, while the standard deviation controls the amount of blur applied to the image.