Valances are made of fabric. They're often hung on a separate rod that extends farther out from the window than the curtain rod, to give clearance. Some valances are attached to the curtains so that a separate rod isn't needed, and others are attached to a valance board that sits above the window.
Valances can be made in a variety of shapes. A bell-pleated valance has an evenly spaced number of gathers with flat spaces between. The gathers are narrow at the top and wider at the bottom to form the "bells." The pleats on a box-pleated valance are uniform, with narrow spaces separating them, and are the same width at the top and bottom. A box-pleated valance has a more formal look than softer, draped valances.
Serpentine or scalloped valances are gathered, with curved bottom edges. The serpentine dips lower on the sides of the window, then rises to a straight edge in the middle. The scalloped valance has a series of curves along the entire bottom edge and can be one length or longer on the sides, as well.
Balloon valances are sewn in a circular pattern with a rod pocket and form softly draped circles when placed on the rod.
Cornice boards are made of wood, foam or cardboard and covered with fabric. They're attached to the wall above the window. Cornices usually have a more tailored look than valances, since the fabric is attached without gathering or ruffling. A striking fabric pattern will be displayed to better effect because there are no folds to obscure it. The cornice can be designed to accentuate the shape of the window. For example, an arched window can be topped with a cornice that follows the line of the arch. Cornices can also be cut in fanciful shapes or accented with tassels, fringe, beading or trim.
A swag looks like a very long, wide piece of fabric that's gathered at each top side of the window so that it forms one large scallop in the middle and hangs down on each side. In reality, the center section and the sides, which are known as cascades, are sewn separately. They're then attached to a valance board that's mounted over the window.
A fan-shaped swag is a variation on the traditional scalloped-shaped middle section, with pleats at its center to give it a fuller look.
Swags are also made, very informally, with sheer scarves draped over decorative rods. They're usually used alone.