The process of filtering refers to the removal or separation of unwanted materials from a mixture, often using a porous material that allows certain substances to pass through while blocking others. This can be done manually, such as with a coffee filter, or mechanically, such as with an air purifier that uses filters to remove dust and allergens from the air. Filtering is commonly used in various industries, including water treatment, food processing, and manufacturing, to improve the quality of products or processes by removing impurities or contaminants.