Single hung windows have two sashes, an upper and a lower. On single hung windows only the lower sash operates, moving up and down.
Double hung windows have two sashes, an upper and a lower. On double hung windows both the upper and lower sashes operate, moving up and down. Many Wood windows allow for the sashes to tilt inward for easy cleaning.
Casement windows are hinged on one side, allowing for a crank to operate the window and open like a door to the outside.
Slider windows consist of two or three panels. At least one panel - and sometimes more - operate by sliding on a track back and forth.
Bay windows consist of three panels, two set at 30, 45, or even 90 degree angles and a large center panel. The whole unit projects outside the wall, creating a nook or sitting area on the interior. Bow windows are similar but have more panels, creating a larger cove.
Awning windows are horizontal windows that are hinged at the top, allowing for operation by a crank.
Picture windows come in a variety of shapes and sizes. Picture windows are fixed and non-operational.
Hopper windows are similar to awning windows except that they are hinged at the bottom and operate manually by pulling them inward.
Specialty, or geometric windows, are any type of window that is not rectangular. Some may operate, but most are fixed and non-operational.