Bootcamp allows you to partition the Mac hard drive and install a legal copy of Windows on it (which you have to buy). You then have both MacOS X and Windows on the Mac. When you start it up, you chose which operating system you want the Mac to run in. With Bootcamp, it's one or the other. With the software called VMFusionware or Parallels you can run both operating systems at the same time, transfer items between systems, see both screens etc.