Heard of conditioner washing? If not, it's simple: it's just a way to cleanse your hair without shampoo. You use conditioner instead.
Some people do it exclusively, but you don't have to (because I know someone out there is groaning at the thought of never using shampoo again). Daily shampooing is usually too harsh and drying for black hair, so if you exercise frequently and sweat, or if you just like styling your hair while wet and do it every day, you may want options outside of a typical shampoo-and-conditioner session.
This how-to on conditioner washing can give you some tips. Remember, you can co-wash once per week or on an as-needed basis. I shampoo about once a week but if I need to cleanse my hair in the meantime, I co-wash, air dry and go.