Both BBL and laser use high-energy light to target skin structures such as hair follicles.  Laser uses light of a single wavelength, whereas BBL uses light with a range of wavelengths.  The end result is similar – light energy gets converted into heat and destroys the fair follicle target.  Early versions of IPL were often inferior to laser but the new generation BBL can achieve similar results with the advantage of being faster, less painful and more effective on lighter coloured hair.