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
Know your hair type and be realistic about what hair styles work best with it. Don't agree to a new hair style that you know in your heart will be impossible to duplicate at home.