Because I don't really know about SOPA (Stop Online Piracy Act) and PIPA (Protect IP Adress), so I won't talk too much. All I know about it is when the US senators (republican and democrat) has the same voice against internet products' piracy and infringement around US (downloadable free music, films, etc. that doesn't have any legal permission to be downloaded.
Anyway, what are SOPA and PIPA means?
According to their origins, SOPA a.k.a House Bill 3261 / H.R.3261 is a bill that was introduced in House of Representatives of US on October 26, 2011. As cited in Wikipedia.org, the bill, if made law, would expand the ability of U.S. law enforcement and copyright holders to fight online trafficking in copyrighted intellectual property and counterfeit goods.
Then, what is PIPA? PIPA a.k.a Senate Bill 968 / S. 968 is a proposed law for the copyright holders and U.S. governments to limitate access to "rogue websites dedicated to infringing or counterfeit goods", especially for the sites that registered ouside the United States. It was introduced on May 12, 2011. So we know that PIPA came first before SOPA, because it is as a rewritten former proposal of Combating Online Infringement and Counterfeits Act (COICA) that was failed to pass in 2010.
