I can explain series and paralell to you, but that's about it, OK, series is when the - of one runs strait into the + of the other, the way to work out the resistance/impedance here is to add them, so a 4 ohm and a 4 ohm would make 8 ohm.
Paralell is where the + of each are connected and the - of each are connected, both being connected to the same source. The way to work it out here is more complicated but assuming they're both the same it gets halved, so if you have two 4 ohm speakers it becomes 2 ohms. It's different if they're not the same, the formula is 1/RT = 1/R1 + 1/R2 where R1 is the first speaker, R2 is the second and RT is the combined resistance/impedance, basically it drops.
Hope that helps a bit.
