In the early 80's, there were a lot of home computers. A Japanese company called ASCII corporation (directed by Kay Nishi) decided to create an industry standard for home computers: MSX was born. MSX means Machines with Software eXchangeability. This is the true and only meaning, stop spreading the word about another explanation please.
The new standard was based on an existing computer: The Spectravideo SV 318 which can be considered as a beta version of MSX1 computers. Microsoft designed then MSX1 computers and the first version of the OS: MSX DOS 1 (which looks like early versions of MS-DOS).
Almost every Japanese and Korean computer companies made their own MSX computers (except maybe NEC). Bill Gates was then very confident about the future of the MSX standard.
Spectravideo (one of the MSX companies) made an 80 column card and adapted CP/M for the MSX.
A lot of programs (especially a lot of games from Sega, Konami, Taito, ASCII, etc.) and hardware were developed for this standard. Despite all its qualities, the MSX family didn't have great success in USA. However it was pretty well known in Europe (particularly in the Netherlands and France), in South America (Brazil specifically) and Russia (then the USSR). This standard was replaced in 1985 by MSX 2.
BUILT IN LANGUAGE
Microsoft Extended Basic (MSX Basic V1.0)
At least 70 keys (including 5 F-keys with 10 functions and 4 arrow keys)
Video chip must be compatible with the Texas Instruments TMS 9918/A or TMS 9928/A (Japan : 60 Hz) or TMS 9929/A (Europe : 50 Hz)
At least 8 KB (most machines had 64kB built in)
32 KB BASIC/BIOS ( MSX BASIC V1.0)
Mode 0 : 40 x 24 Mode 1 : 32 x 24
Mode 2 : 256 x 192 with 16 colors (Hires mode) Mode 3 : 64 x 48 with 16 colors (Multi colour mode) 32 sprites
General Instruments AY-3-8910 Programmable Sound Generator 3 channels, 8 octaves
Joystick socket (1 or 2), Cardridge slot (1 or 2), Tape-recorder plug (1200/2400 bauds), RGB video output, Centronics interface