It's an educated guess since the software developers don't seem to think it's necessary to explain revisions or to keep the Help up to date but here goes. I think requery was designed to address the problem of downloading very large files, like movies. When a big download tanks midstream requery kicks in and keeps the request alive and can resume the download if the file becomes available again. I've left the program running all night and had big movie files resume and load long after the older versions would have quit and shown "Could Not Download". So if you can walk away from the machine and just let things run you have a better shot at these monster files. I've also had some luck resuming a download that's in an interminable 'requery' with Repeat Search. If the stalled file shows up in the repeated search you can kill the stalled download and then request the same file from the new search. They actually resume where they left off.
Do you know anything about "Metasearch"?