Why NZB? When a very large file attachment is posted to a Usenet newsgroup, it is usually divided into multiple messages or parts, because there's a limit to the size of each Usenet posting.

NZB file formatting lets you retrieve these multiple, separated parts from the Usenet in one go in the most automated, streamlined manner. Imagine, before NZB came into existence, people use to look up and upload individual file parts manually and virtually combine the file themselves.

These days, to download such large file, simply look for a file that is already formatted into an NZB file. A top newsreader, such as Newsleecher for PCs, and Unison for Mac, usually features thorough indexing of NZB files, so make use of this index for searching. Click a button, and your newsreader will download and decode all the bits on your behalf.
You can also search for NZB files using online Usenet search engines such as:

Binsearch http://www.binsearch.info

Asianusenet http://asianusenet.com/

After downloading the NZB file(s) from these sites, just open the file with your Usenet program and the files will start downloading immediately.
Giganews Newsgroups