Furniture items have a special place in Final Fantasy XI, and provide bonuses not found anywhere else. These furnishings items are only useful when placed into a character's Mog House. There are three benefits from having furnishings in your Mog House:

Furniture items are displayed when placed in the Mog House, providing a customizable area within FFXI.
Extra Storage is provided by furniture, providing extra space to hold rarely-used items.
Special key items called Moghancements are provided by having furniture in your Mog House. Many of these Moghancements give bonuses not available from anything else in FFXI.
The first two benefits listed above are only available to a character who is in his home town; neither the display of furniture or items in Storage can be accessed from a Rent-a-Room or Nomad Moogles. Since most characters level 20+ spend the majority of their time based in Jeuno,

this limits the usefulness of furnishings to primarily being based on the Moghancement that they provide. (Note that furniture is also required for gardening in FFXI; details about this can be found in the FFXI Gil Gardening Guide.)

Furniture items are utilized by putting them into the safe in a character's home city Mog House. Once a furniture item is in the safe, the Layout option on the Mog House menu can be selected to arrange the furniture pieces inside the Mog House. This provides a top-down view of the Mog House, with a grid provided to allow easy arrangement of the furniture items. There are a total of 336 floor spaces where furniture can be placed, along with 5 wall tapestry spots. The wall furnishings are hung up, and do not take any regular floor spaces.

The size of furniture is displayed in the list of furniture items at the bottom of this guide, providing information how many spaces each piece takes.

Some furniture items can be stacked on each other, as listed in the Placement field; the furniture marked Top can be put on the items listed as Bottom.