A rinse, when you aren't referring to temporary hair color, is any liquid that you pour over your head and let sit before you wash or rinse it out. The most common type of rinse is a black tea rinse which is used to strengthen the hair much like a protein treatment. The usual method of doing a tea rinse involves boiling a pot of water with up to 10 bags of tea, letting it cool over night, and then pouring the pot over your head. I don't use this treatment, but I bet it could become costly and cause a lot of your money to go literally down the drain!
I suggest brewing a single cup of tea with more than one tea bag, letting it cool, then pouring the tea into a spray bottle. Apply the rinse by spraying it all over until hair is completely saturated and let it sit. Using this method ensures that the hair is thoroughly wet, there is no mess, and no tea goes to waste.