There are two possibilities to download binaries from the Usenet. The first one is the most common one. You download the headers of a newsgroup that you are interested in and select the files that you want to download. All of this is done in your newsclient. This method has some serious disadvantages.
You may not search through many newsgroups at once for instance or search for files in a large list of groups. Usenet indexing sites try to aid users by offering a way to search the contents of many newsgroups at once. They index new posts that appear in the observed groups and offer web interfaces that users can use to search for files.