It was an type of personal computer produced during the 80s, like the Commodore 64 and others. Saw usage in Europe and much wider usage in Japan. Received quite a lot of games, and it's where Konami first really took off - the "real" Metal Gear and Metal Gear 2 were both on MSX variants. There were quite a few original games for it, as well as lots of ports. I believe it was substantially more suitable for action games than it's main competitor, the PC-88 (and eventually 98). Anyway, you can read all up on it at Wikipedia:
While it still has a fair share of enthusiasts with hardware, most enjoy it now through emulation or special digital distribution services like the Engrossing Game Gallery. Actually, there was a special partnership with the people behind Project EGG and some other dudes to produce English versions of classic MSX games and make them available for download (at a price) called WOOMB, but it's apparentlly caught in legal issues...?
That said, McCall...do you find those versions of the Ys games satisfactory? And while I can recognize getting Hydlide 3, isn't Hydlide 2 supposed to be about as bad as the first one?