Used as a verb it means to bleach the hair and remove current color.
When used as a noun it refers to the chemical composition designed to remove color from the hair. Bleach is sometimes referred to as a pre-lightening or decolorizing treatment.
Daily Hair Tip
If you lie on your back while you sleep this could cause hair stress leading to split ends in the back. To avoid hair stress tie hair back using a soft scrunchie band.