There is no such thing as a stupid question.  It is only stupid if you don't ask the question so you can get the answer!

CO'ing is referring to Conditioner Only washing.  Many people with dry and/or curly hair (which tends to be drier than straight hair), find that using just conditioners to clean the hair is less harsh on the hair.  Many conditioners have the same cleansing ingredients as shampoos, just in lesser concentration. 

If you decide to try this method - be aware, that it takes a while for the hair to "adjust" and you may feel your hair is not getting clean - and it looks greasy all the time.  This is due to not using as much of the detergent/soap that strips the hair of the oils.  When the shampoos remove all the oil, the scalp then produces more oil to replace it.  It can take a few weeks to a month for the scalp to figure out that you are not removing as much of the oil and quits producing as much oil.  The same is true when you start trying to length the amount of time between shampoos. 

Hope this answers your question!