Filter
A general term for processes that apply specific effects to an image, including blur, sharpen, sepia, and mosaic among many others.
A filter is a mathematical operation applied to image pixels to alter their appearance. Filters range from Instagram-style presets that change the overall mood of a photo to specific image processing operations like Gaussian blur.
Common filter types include blur (for noise reduction or background softening), sharpen (edge enhancement), sepia (vintage color tone), and mosaic (privacy protection). Technically, most filters use convolution, which computes new pixel values by referencing surrounding pixels.
The mosaic tool applies blur and pixelation for privacy protection. Applying a sharpness filter can enhance edges in slightly out-of-focus photos. Best practice is to apply filters non-destructively so changes can always be reverted.