Technically, there are more, but we will not get into the various combination at this time. The first is full height, one tier, shutters with no division. This describes shutter units that extend from the bottom of the window to the top with a single bank of louvers (minus the top and bottom rail).
There are four ways to vertically configure your interior window shutters.
A single tier shutter unit can also be constructed with a divider rail. A divider rail looks much like the top rail, only it is located between the top and bottom rails. The location of the divider is often in the center of the panel, but it is not required.
Double tier shutter units use two shutters from top to bottom. The shutters swing separate from one another. This configuration is often used to open the top shutters and keep the bottoms in a closed position for privacy.
The above picture features a double tier traditional shutter unit stained in a dark finish installed during a beautiful bathroom remodel.