Before we get into the nitty-gritty of different window treatment styles let me first provide you with a window primer.

A window is an opening in an otherwise solid and opaque surface that allows the passage of light and, if not closed or sealed, air and sound. Windows are usually glazed or covered in some other transparent or translucent material. Windows are held in place by frames, which prevent them from collapsing in. Wikipedia.

common window types:

Awning -- A window with a single sash hinged at the top to open up and out from the bottom.

Casement -- A window with a single sash hinged on the left or right that opens out with a crank or lever. Casements provide maximum ventilation.

Double-hung -- A window with two sashes that bypass each other vertically when opened from the bottom and top.

Fixed glass or Picture Window -- A window that does not open. They come in a variety of shapes to combine with other windows. Large fixed windows are often called picture windows.

Gliding or Sliding Window -- A window with two sashes that move horizontally in a common frame.

Simulated divided light -- Any window with muntins affixed to the inside and outside of a panel of glass to simulate the look of true divided lights. Snap-on grilles can be removed easily to clean the glass.

Single-hung -- A window that features an upper and lower sash, but only the lower sash is operative.

Specialty -- This term refers mostly to unusual shapes, such as triangular, round, half-round, and other nonstandard configurations, including bow and bay windows. Most are fixed-sash (inoperative) and are included to create architectural interest.

Tilt -- A double-hung window with sashes that tilt for cleaning.

True divided light -- Any window with multiple individual planes of glass assembled in the sash using muntins.

Transom window -- A window above a door; if an exterior door the transom window is often fixed, if an interior door it can often open either by hinges at top or bottom, or can rotate about hinges at the middle of its sides. It provided ventilation before forced air heating and cooling.

Jalousie window -- Also known as a louvered window, this window is comprised of parallel slats of glass or acrylic that open and close like a Venetian blind, usually using a crank or a lever. They are used extensively in tropical architecture. A jalousie door is a door with a jalousie window.

Clerestory window -- A vertical window set in a roof structure or high in a wall, used for daylighting.

appearance and style:

• Double-hung and single-hung windows can be found on traditional Cape Cods and colonials, multistory Victorians, early-20th-century bungalows, and other "period" architectural styles. Muntin and grille designs provide strong stylistic cues, but the basic design remains versatile. They are appropriate for all but the most cutting-edge contemporary home designs.
• Casement shapes tend toward the tall and narrow, so wide wall openings usually feature multiples, sometimes with a fixed picture window in the center. Ranch-style, Prairie-style, and other 20th-century home designs often feature this type of window. Grilles will help create a more traditional look, while an unbroken expanse of glass provides a contemporary flavor.
• Awning windows take on a more traditional flavor when fitted with muntins, but look contemporary when unadorned.
• Sliders typically have a strong horizontal orientation, so they often work best with home designs such as ranches or Prairie-style buildings that have strong horizontal lines.
• Fixed-glass windows impart a decidedly modern feel when they're large and uninterrupted by muntins or grilles. Smaller sizes with grilles and appropriate trim can mimic most traditional looks.
• Specialty windows can complement a traditionally styled larger home. On smaller residences, which historically have featured simpler window shapes, specialty windows are more appropriate to contemporary designs.

function:

• Casement windows provide generous ventilation relative to overall window area, because the entire sash swings open. Exposure of the outward-swinging frame can be a problem if rain arrives suddenly. High winds also can be hard on casement windows.
• Awnings, with their horizontal rather than vertical orientation, offer the advantage of shedding water harmlessly if left open during a rainfall. Though they can be used alone, awnings are often installed above or below large picture windows to provide ventilation at the top or bottom of a wall.
• When maximum views are the objective, a picture window offers the least obstruction. Ventilation requirements are often handled by installing operative windows above, below, or alongside.
• Specialty installations such as a bay window provide more light and ventilation in a given amount of wall area; they create a more spacious feel and room for sill shelves, window seats, and other features; and they add a lot of charm besides.
• Test the operation of windows in the showroom or store; they should open easily, quietly, and completely.

additional terms:

Additional Window Terms

Argon -- A gas injected between layers of glass to increase insulation. (Argon insulates better than air.)

Dual-glazed -- A window with two panes of glass, with air or argon gas in between the layers for insulation.

Jamb -- Each side of a window's frame.

Low-E (low-emissivity) -- A coating applied to glass to reflect heat and harmful UV rays.

Muntin -- A strip used to separate glass into multiple lights. (Vertical strips between panes are known as mullions.)

Pane -- The term for the glass part or parts of a window.

R-value -- A window's resistance to heat loss or gain. The higher the value, the better.

Sash -- The framework of the window that holds the glass.

Sill -- The bottom of the window frame.

Trim -- Any decorative, nonessential parts of a window.

Triple-glazed -- A window with three panes of glass, with air or argon gas in between the layers for insulation.

U-value -- The amount of heat escaping through a window. The lower the value, the better.