The purpose of CivHack is, logically, to enable you to hack the game Civilization. It allows you to alter the characteristics of military units, terrain squares and city improvements. As an example, let us say that you want your Settlers units to be able to move 30 squares per turn. You could do that in about 2 seconds with CivHack. Or, if you think that Horse squares should have 12 Food, 8 Production and 9 Trade - no problemo. CivHack, put simply, puts you in a position as close to being God <in the context of the game> as is possible. Beware though, any chages that you make for your own benefit also benefit your opponents!