Yep, what @TSR Campers said. The borax acts as a water softener and releases disolved oxygen into the water aiding the non stinky biological activity digest stuff. The Dawn is a detergent that helps break up solids and emulsify oils/greases. Many other additives do the same at a higher price point while others surpress or stop biological activity but don't disolve solids or clean.
TR Bolin did a great YouTube video on this method. He explains it accurately.