Essentially they're trying to say the same thing. If the "subwoofer out" connector on your receiver is a regular old RCA jack, then you need a single (mono) RCA cable (as opposed to a stereo one) to run from there to the RCA input on your sub. Some cable companies make special LFE (low frequency effects) RCA-type cables, and they might charge a premium for them. This level of spending is mostly marketing hype, however, and any decent RCA-type cable will do, as long as it's of decent quality and construction.