Floetrol is an additive you put in latex paints that changes the chemistry enough where your paint doesn't have any brush or roller-marks. It's like a white liquid (that shouldn't change your color) that you have to mix with the paint until the color disappears so everything is even. While some painters can paint perfect, when you don't have years of hands-on experience this does help make up for the gap. You only need a little bit (5-8 ounces) per gallon so you can make it go fairly far. I've always been really happy with it.