Catholics believe we are judged immediately after we die (Particular Judgement). Some of us will go to heaven. Then there is still the Last Judgement (or Final Judgement). What effect does the Last Judgement have on those who are already in heaven? Will anything about their existence change? The only thing I could find in the article I linked to says that their sins will be made known. Is that all that happens?
Basically, when you die, your soul goes to a place prepared for it, but your body is still here.
So, as was shown with Lazarus and the rich man, you may be in Abraham's bosom, which is a good place, or in Hell, suffering.
But, this is just your soul suffering.
At the final judgement your body will also be with your soul, and you will be judged for the final time, and your body and soul will have the reward or punishment for it.
Whether the place that was prepared for the soul is actually in Hell is not necessarily a closed discussion, as Aquinas states that until the final judgement we will be in Hell, but Abraham's bosom won't involve the suffering that the part in Hell would be.
But, there is also a possibility that our soul will be in Heaven. Either way can be argued, you can read the links below and come to your own conclusion.
An easier to read description of what is going to happen:
The official teaching on the
The official teaching on the Final Judgement: http://www.scborromeo.org/ccc/p1s2c2a7.htm
Thomas Aquinas on where souls go after death: http://www.newadvent.org/summa/5069.htm#article1