A leave in conditioner is a product that you 'leave in' your hair, to help condition dry, moisture-starved, dull, damaged hair. There are several ways to use a leave in conditioner, most commonly, you can apply a few spritzes after your shower (on wet or dry hair). Leave in conditioners are a great option to add shine, moisture, hydration, and more, leaving your hair looking and feeling its best, all day long.