Here's Wikipedia's take on Ramadan:
http://en.wikipedia.org/wiki/RamadanI haven't had a chance to go through and check their sources, but I suspect that it's a very good, albeit basic, outline -- at least, if their Muslim fact checkers are about as good as their Jewish fact checkers.
It was explained to me once that Ramadan is for Muslims like Simchat Torah is for Jews -- a celebration of the occasion on which the holy text was revealed to the people (Jewish) or to the prophet (Muslim). The Muslim calendar is lunar and therefore not seasonally fixed, so while the Muslim month of Ramadan doesn't change, it does march backward through the secular months, so that one year Ramadan takes places in the early spring, and the next year it'll take place in the late winter.
So, yay! Happy Ramadan to all the Muslims who read this. May you have an easy fast, and I hope you have a fantastic Eid.