DDR (1/2 &3) memory modules for PC's operate with a 64bit wide parallel bus. Dual channel means your motherboard has a pair of 64bit memory busses acting as a single fast 128bit wide bus.
Yes its parallel.
RIMM memory modules are parallel to, but they use a 16bit wide bus (although wider ones were/are made). In theory its a simpler bus allowing for high clock speeds, but the narrow bus adds latency to every transfer.
As the linked website says though, FB-Dimms are serial, but most PC's dont use them, and they dont offer any performance advantage over DDR3 at the moment. Perhaps in the future at much higher clock rates.