The Falun Xiulian Dafa, commonly Falun Dafa or Falun Gong, is a way of cultivation (of the self) and practice.
It means that we have some exercises (five, in the form of qi gong exercices) which aim to purify the body, making you feel energised and free from diseases.
I personally think these exercises are very very powerful.
The real aim of the exercises, anyway, is the gradual transformation of the body in high-energy substance.

The 5 exercises are just a little part of the Dafa.
They are just the "practice", in "cultivation and practice".
So, what's cultivation?
The cultivation is a process in which the practitioner loses his material desires and emotions (but not necessarily his material assets) to assimilate himself to "Zhen-Shan-Ren" (Truthful - Compassion - Tollerance) which we consider the highest essence of the Universe. You don't necessarily have to lose concrete things, because this is not an out of the society practice :)
The better you cultivate yourself, nearer you are to the ZhenShanRen standard, and more elevated is your understanding.
So everything I say is what I can understand at this level of comprehension :)

I just spent a few word to describe it in a general way, but there really are lots of things to say ^^

It's important to say that the main book of this discipline is Zhuan Falun (you can easily find an ebook on internet). May I post the link?
Also I would like to post the exercises' videos as well, if you're interested (maybe in the qi gong area) ;)

I'm here for any questions / doubts etc. :)