Door furniture or otherwise called "door hardware", are fixtures attached to the door, which basically include items such as door knobs, door handles, door locks and so forth. Door fixtures are generally used to enhance the functionality of the door, to make it better, more secure and more efficient.
Some common items that you can find under the door furniture category will be:
A door hinge is a flexible joint that connects the door to the wall which basically allows the swinging motion or rotation of the door (while opening or closing it). They are usually made of metal materials such as brass or steel.
A door handle, or sometimes being replaced by a doorknob, acts as a grip to the hand when opening or closing the door. It is perhaps the most visible part of the door, which is why many people are aware of its importance in interior design. The style and quality of a door handle may just affect the entire atmosphere of the interior so choosing a suitable design of door handle is really important during installation. A sleek, stainless steel door handle, for instance, is suitable for modern home designs.
Locks are very important security feature for the door and your home. It prevents burglars or intruders from sneaking into your house, ironically, it also prevents your kids from "sneaking out" of the house. There is a wide variety of security options that you can find in a modern door lock. While gaining access through conventional door locks requires only the key, modern digital locks may require a password or even your fingerprint.
All in all, it's the "Quality" of the door furniture that makes it worth buying. Apart from its aesthetics, higher priority should be given to the functionality, practicality, durability and usability of the furniture.