Draperies should not be confused with curtains. Curtains are lightweight, flat panels of fabric covering a window. Draperies are heavier, longer and pleated. The pleating helps the draperies maintain their shape when they're opened and closed. Weights sewn into the bottom hem help to keep the draperies straight. When hanging draperies, you'll need a special rod to support their weight and help them to open and close easily.
Valances are the decorative coverings at the top of a window treatment. Some draperies or curtains have a built-in valance sewn into the top. Most treatments will require a separate valance. This valance will need its own rod to hold it in front of the rod supporting the draperies. Specialty rods are available to maintain the full shape of balloon or puff valance, but stuffing the valance with tissue paper is a substitute support.
A double rod consists of two narrow curtain rods, one in front of the other. The small size of the rods makes them best for supporting lightweight curtains on the smaller rod and a valance at the top of the curtains. Curtains are meant to hang closed because they don't have pleats like draperies. Without pleats it requires a lot of effort to reset the curtains after opening or closing them so they hang neatly. This is why curtains are best for a double rod. The rod doesn't have the pulley system of a traverse rod because the curtains hanging from the double rod are meant to be left closed or manually pulled to the side and held with tiebacks. If you have lightweight draperies and don't plan to open them very often, you can use a double rod, but it's not the best hardware for the job. For heavy draperies, look for a traverse rod.
You'll need a traverse rod to support the weight of draperies and to provide a way to open and close them. Hang draperies by hooks from the traverse rod. The hooks let the draperies glide smoothly along the track when being opened and closed. Place a second, slightly longer rod, in front of the traverse rod for the valance. The valance should extend beyond the ends of the draperies and around the corners of the rod to the wall. This gives the window a fully dressed appearance.