Window treatments can speak volumes about the mood of a room. They can hang freely, or be tied back in a variety of ways. They can be informal and casual or formal and polished. Knowing the differences can help you decide which look is best for your home.

Tying back curtains above the halfway point of a window is called a "high tie". Curtains tied with a middle tie are tied back at two opposite sides at the center of the window. The low tie is used to secure a curtain about three-quarters of the way down. Sometimes a center tie is used, which brings the drape into the center of the window, generally toward the lower part, and tied with a ribbon or tie back. The criss-cross tie is used when two overlapping panels are each pulled back to the opposite sides of the window. Depending on the fabric they're tying back, all of these tie back options can give a formal or casual look to a room.

The tie backs themselves can also make an impact, and change the feel of a window treatment. You can tie back with ribbon, satin tassels or fabric that matches the curtains. You can also use metal U-shaped hardware that is affixed to the wall. The curtains are simply tucked into the U and arranged to create a pleasing appearance.

Though choices for window treatments are endless, most curtain styles fall under two categories: formal or casual.

Formal window treatments, called "draperies", are generally hung in layers, with panels, shades or blinds under heavier panels. The panel is generally a light-diffusing lace or sheer linen, topped by a heavier pleated drape, which usually hangs to the floor. They're hung from a curtain rod, and may be opened by a cord pulley mechanism. These may be topped by a valance across the top of the window. This covers any hardware or rods, and gives a finished look to the window. These are usually found in formal living rooms or dining rooms, and have become less common with the advent of more casual, usable living spaces and easy-care home design options.

All other types of window coverings are informal. They may employ one or two layers, and aren't usually lined. These types of curtains are lighter in appearance, and can be used to dress a window up or down.

Whichever window treatments you choose, you're sure to find that the way you accessorize them is just as important.