Bonjour is a network discovery technology developed by Apple, Inc. It allows computers and printers to automatically find and connect to each other's services using a new communication protocol, saving time and simplifying tasks such as file sharing and setting up printers.
Apple computers running newer versions of Mac OS X support Bonjour as a capability embedded in various network applications such as the Web browser (Safari), iTunes, and Back To My Mac. Additionally, Apple provides a Bonjour service for Microsoft Windows PCs as a free software download on apple.com. The technology is based on Internet Protocol (IP), allowing it to work with both wired and wireless networks.
→ More - Bonjour - Developer Connection (apple.com)

I have Windows XP-2 Home Edition. Do I really need Bonjour? Why?
You don’t need Bonjour. It’s a piece of Apple “bloatware” that sucks down CPU cycles needlessly. Offers very little return for its investment.
Bonjour can cause network issues on Windows, stopped my computer seeing the internet. Disabling it fixed the network problem, see windows7forums.com/windows-7-networking/7408-fix-unidentified-network-no-internet-access.html
I have a dell computer and wireless printer, both new. The network printer frequently does not work. I receive messages that say BONJOUR has stopped working. I assume this is what why it will not print . How does one fix this issue… It tell the file causing problem is in DNSResponse.exe. I am not good at computers anyone tell me what to do it is frustrating
Thank uyou
Causes Windows7/Vista network problems.
I.e. your network card cannot connect to the router.
Drove me foookin mad for months