In simple terms, a grid of metal bars, typically shaped in an inverted Tee form is hung from the building original ceiling or ceiling framing. The supporting grid is usually spaced two-feet on center to form square openings, or to form two-foot x four-foot rectangular openings into which are "dropped" prefabricated ceiling panels that are offered in a very wide range of designs and materials.
The distance between the upper surface of the suspended ceiling grid and the surface of the original ceiling can vary very widely, but in order to install the ceiling panels, manufacturers specify a minimum distance, typically 2" plus the thickness of the panels themselves, or a minimum distance of 4”. Suspended ceiling systems utilize a metal T-bar grid supported by wires from above.
Advantages of suspended ceiling systems include relatively good acoustic properties, ease of removal to access things above the ceiling, and individual tiles can be replaced readily. On the downside, suspended tiles lower the ceiling at least two to three inches.