Most powders can be used two ways: as a presoak (mix the powder with water per the product label and soak items) or added directly to the washer drum with your regular detergent. Many formulas are labeled safe for both High Efficiency (HE) and standard machines.
Some powders are formulated to eliminate odors such as sweat and musty towels. They can be used as a presoak or added to the wash as an in-wash booster to work alongside your regular detergent to reduce odors and freshen fabrics.
Products describe removing everyday dirt and tough set-in stains generally, and some list many specific stains such as oil, grease, coffee, wine, chocolate, ketchup, berries, fruit juice, grass, mud, blood, ink and washable paint.
Many powders are labeled for use in both High Efficiency (HE) and standard washing machines. Some product descriptions explicitly state they work in all temperatures, including cold water.