The tracks distributed on this site, even those labelled "single tracks," actually come as zip archives containing a variety of file formats, track lengths, looping options et cetera. So, when you download a "single track" and find a 40MB zip file downloading, don't be alarmed. This is normal. Here's a run-down of the various formats you'll have to choose from:
The whole track - intro, main body, maybe an extra loop, ending. A better fit for non-looping playback and suitable for listening. Ogg Vorbis version includes loop comments, so in RPG Maker and any other engine made compatible, will play intro once and then loop seamlessly.
Designed to loop as seamlessly as possible in any environment, with no intro or ending. Minimal length and thus file size, but may end too abruptly for non-looping playback.
Ogg Vorbis only. Like full track, will play the intro once and then loop seamlessly in any engine made compatible with LOOPSTART and LOOPLENGTH comments, such as RPG Maker, but only includes one loop and no ending, to save on file size. May end too abruptly for non-looping playback.