If I'm understanding right, you're asking why Roe v Wade was controversial. Um. The Supreme Court decision on that case gave women the legal right to an abortion. (Or, I think more precisely, declared that women had a constitutional right to an abortion.) Now do you understand why it was controversial? (One of THE most controversial SC decisions ever.) I mean, before that decision, most women were consigned to back-alley butchers if they wanted an abortion. (The rich, of course, have always known how to get what they want, no matter what.)
So-called pro-lifers have actually curtailed women's rights to an abortion through harrassment and threats to doctors who are willing to perform abortions, and even through clinic bombings. But technically, the Supreme Court decision still holds.
If Roe v Wade was overturned ... well, I'm sure you can figure out what that would mean. This is one reason why many people are concerned about who gets on the Supreme Court. Those justices can make a big impact on people's lives in the US. (Hey, just look at the Gore/Bush election ... if you want to call that an election.)
Check out wikipedia. For sure, there has to be a lot about Roe v Wade there. You might also check about.com. If you simply googled Roe v Wade, I'm sure you'd find plenty of info.
Hope this helped. (Hope I understood you correctly.)
PS. I decided to check out wikipedia myself. Technically, the decision was based on the constitutional right to privacy, which meant that state laws banning abortion were unconstitutional. LOTS of info. Check out it.
http://en.wikipedia.org/wiki/Roe_v._Wade