One of the main advantages of using detergent instead of soap is that detergent is less likely to produce scum when combined with hard water. Detergent is also more effective for cleaning modern clothing fibers.
Although some people use the terms soap and detergent interchangeably, the two products have different chemical properties. Soap is made from animal fats or vegetable oils, while detergents are made from the byproducts of petroleum. Detergent molecules are also able to break up oil droplets, making them very useful for cleaning grease stains from clothing. When oil droplets and detergent molecules mix, they form an emulsion, making them easier to wash away from fabrics.