As fake as ballet or gymnastics, but no more so. It's choreographed and pre-scripted, but the actual physical stunts are generally real (and take considerable skill). But they're not really trying to hurt each other, if that's what you're asking--in fact, they work very, very hard to make sure they don't hurt each other, and often injure themselves in the process.
yes it is fake I saw a match on TV (i don't who were fighting) and one was kicking the other and the cameras were at the right angles and i saw that his feet was not touching the other ones body. that means its fake and scripted.