Curtains and curtain panels are synonyms. Curtains usually do not have linings and are hung from a rod by tabs. They are mostly light weight and can be used as a decorative piece. Curtains are casual and easy to make. The length of the curtain panels only depends on where you are using it. It can be floor-length or short that can cover the window. When you start to add linings to curtains, it will start to appear more like drapery panels. Drapes and drapery panels are the same, and they are usually lined and cover the length from the top to the floor. They are often attached by hooks to a traverse rod. They are heavy weight. A cord can be used to draw both of the panels open and closed. Drapes are more formal and stylish unlike curtains which you can just open and close by hand. In general, drapes are pleated. When it is fully open, it may still take up some space of your window view. You should estimate the width that the fabric occupies at opposite ends of the window when they are fully opened. Finally, the key difference between drapes and curtains is very simple. Basically, drapes are pleated and are more formal. Curtains are informal and it can be easily made. Both can make the window more appealing with extended flows of fabric.