The difference, traditionally, has been that Japanese RPGs have been derived from the system that Dragon Quest introduced, while most western RPGs have been based upon the system that Dungeons & Dragons introduced. Over the years, the two have begun to meld into each other, but the split is still fairly apparent in one respect: JRPGs are almost universally simpler in gameplay interface than WRPGs.
In the early days, the split between JRPG and WRPG was very obvious, of course, because JRPGs were all very simple and WRPGs were almost universally complex (certainly compared to JRPGs). As I said, however, the two types have had a bit of a melting-pot effect towards becoming like one another.
SRPG is short for Strategy RPG. That's an entirely different kettle of fish, and what you might even call a prototype melding of WRPG and JRPG on neutral grounds. I'll let somebody else go into detail about them, however.
Sky Render - Sanity is for the weak.