The document discusses different types of mean filters and order statistics filters used for noise reduction in images. It describes four types of mean filters: arithmetic, geometric, harmonic, and contraharmonic. The arithmetic mean filter computes the average value within a window. The geometric mean filter takes the product of pixels within a window. The harmonic mean filter calculates the inverse average of inverse pixel values. The contraharmonic mean filter uses a parameter to reduce salt and pepper noise. Order statistics filters like the median filter replace pixel values with the median within a window, effectively reducing noise.