Bonjour used to be known as Rendezvous.  It is based on Zeroconf's discovery service that Apple trademarked and began to develop on its own.  Basically, Bonjour locates multiple devices on a given local network utilizing DNS.  While it is initially installed on Mac-based operating systems X and up, it can also be installed on Windows machines via the iTunes software.

When running, Bonjour seeks out other devices – mobile or otherwise – on a local area network (known as a LAN.) When run with Mac OS, it sets up an actual network between computers without much configuration. This allows multiple computers to share files, music, photos and more without much work. This is especially helpful for computers users who may be worried about the task of setting up such a network.

For example, iTunes will try and locate other users on the network using the software to help share music with one another. Another example of Bonjour in action might be between TiVo desktop units, when one is discovered and then another, both users can share media libraries. Other programs that are utilized by Bonjour included Gizmo, Skype, Proteus and certain Adobe Systems. The Bonjour Browser or iStumbler can be used to sort out the different services, applications and users on the network and how they interact with one another over the network.

Unless your network utilizes more than one computer, Bonjour is an unnecessary component to a LAN.  For Windows users, Bonjour may seem daunting in the face of how a network might be set up already.  If that is the case, diving into using it may not be the best course of action.  However, when looking for a way to organize and truly connect computers on your LAN, Bonjour is an excellent discovery service for users who want to get more out of what they share on their network.