"4X" Strategy game and game released when?

[g_storrow]

I have been reading a little about this game and it says it is '4X' strategy game. I have played a few strategy games but I have never come across the term "4X", what does it mean?
Looking on different websites some seem to say it came out in 1994, GC2 came out in 1995 and GC gold came out in 1997. Then I have read somewhere else February 25th, 2003. I have downloaded the demo version from download.com where one of the comments said not a bad game but I am not paying $40 for a 1995 game.
Cheers in advance
G

[Spaced Cowboy]

explore
expand
exploit
exterminate

(and for MoO3 experience Ha-Ha)

[asleepathewheel]

hmm

It was released in, IIRC March of 2003, I think what you might have seen was what the game was based off of? not really sure.