One of the most common terms we hear is “bifold shutters”. Most often, but not always people are describing a four panel shutter unit. Of the four panels, two panels hinged together with a hanging hinge on the left side of the left panel that attaches to the side of the window opening, allowing the shutters to open to the left side of the window. There are also two panels with the same configuration that open to the right side of the window.
Unfortunately, the term bifold shutters (or bi-fold shutters) does not fully describe the full shutter unit. Horizon Shutters uses the phrase four-panel shutter unit instead of the terms bifold shutters or accordion shutters. The shutter unit may also be cafe shutter units (do not extend the full height of the window), full height (shutter panels that extend from the top to the bottom of the window), and double tier (covering the full window with two panels from top to bottom).
Also, a bifold shutter could also describe a shutter unit that only consists of two panels across that open in the same direction.