Chlorine bleach is a 5.25% solution of sodium hypochloride. It is quite powerful and must be diluted with water for safe use on some fabrics. While a dry form is available, the liquid version is the most common.
When chlorine bleach is used in washing laundry, the chemical ingredient oxidizes helping to remove soil and organic matter. It acts as a disinfectant on bacteria and viruses and generally whitens fabrics.