The front of that speaker says powered subwoofer, so the single rca could be connected to a sub woofer pre-out on your receiver (if it has one, didn't look). The other pair of wires are like a normal passive speaker would be connected, i.e. to speaker output terminals on the receiver. Your other speakers are called active speakers in that they provide their own amplification and just need a signal from your receiver....
ps Never mind, didn't think that thru as there doesn't appear to be a power cord for the "built in subwoofer" so suspect that speaker is from a specific set (like a home-theater in a box type setup maybe) and not sure where the power comes from for the "built in subwoofer" now