It is very difficult to categorise Civilization as a game. It could be a strategy game but its rules can be bent as players see fit, something unacceptable in common strategy games. It could be a role playing game but with each player being his own game-master it can hardly be characterised as such. Artistic ability and historical knowledge are basic in order to play it, something very rare among other games.
The following links are designed for players that are already familiar with the game. Its playing rules are too complex to analyze and since the information presented here is incomprehensible to non-veteran players I suggest you leave these links for the experienced.
Thank you