My understanding of hydraulics is pretty limited at this point in life.  I've been looking at newer tractors and have seen a whole bunch of different hydraulic connectors on the back and I honestly don't know what they all are for.  I've got a couple MX magnums that have these fittings and I'm looking at upgrading a 9130 to a newer steiger tractor.  my 9130 pulls our 1200 planter and only has a single extra hydraulic coupler for the motor return that I believe dumps back into the resevoir, but I may not have that totally right. 

If you could, give me an explanation of why there are so many different couplers now and what they're intended use is?  I hear terms such as case drain, load sense, power beyond, motor return, etc and want to know exactly what I'm talking about.

thanks