............... read the damn FAQ for jdownloader..
IT'S JUST A NORMAL DOWNLOAD MANAGER BUT FOR FILEHOSTER LIKE RAPIDSHARE, MEGAUPLOAD and so on..
it has nothing to do with P2P..
If you have the links in your JDownloader Downloadlist, you run the Download and it downloads by itself, if there is a time you have to wait (as long as the filehoster has one) the programm does the countdown to the end and then starts the download, when the first file is downloaded, you have to wait again (yeah it's because of rapidshare again) and it also starts automatically if the time comes and so on..