I'm still new in Civilization 4 and had a lot of questions about playing the game. I'm finding the game to be insanely complicated so please keep that in mind while giving your answer. If you use too much game jargon I won't understand. Thanks for your help in advance.
Question: Coins. I have seen that if I decrease the research I can start saving coins in my treasury. But till now I haven't used them. What is the use of these coins? When do we make use of them really? As beginner should I always keep my researched maxed out (as long as coin consumption is not negative)?