Simplest answer is anything that is done to your body that alters your natural appearance. That can be as mundane as women wearing makeup or having pierced ears, braces and plastic surgery. Yes, those are body modifications, we are just so used to it that no one thinks of them as true modifications. The difference is usually noticed when the piercings are in areas other than the ears or a large amount of them before it is seen as a true modification. Plastic surgery is considered body modification when taken to extremes.
Tattooing, piercing and scarification has been accepted body modification in various countries for centuries. Tattoos have been around for quite some time in the USA but it has been in the last 20-25 years that tattoos are more acceptable with less of a stigma attached to it especially for women. Extreme piercings and scarifications are still generally looked at as taboo in our culture as well as those individuals that choose to tattoo their faces.
Most people consider body modification as anything that is done to your body that is a permanent change. Now there are numerous types of modifications that fall into this category. Tongue splitting, giant lobe rings that stretch your earlobes into the size of tennis balls, cutting designs into your flesh and hoping for raised scar tissue in the shape of the design, these are the more permanent modifications and are still looked upon as taboo. Society as a whole has not embraced these practices.
I am a tattooed woman so I have practiced a form of body modification most women haven’t done, yet I personally would not go as far as some do with tattooing or any of the above mentioned modifications. While I would not do some of these modifications I will stand up for the right of the individuals to do what they want with their own bodies even if I think they are crazy for doing so. Not long ago I would have been looked down upon for having ink, now no one looks twice at me unless it is to check out my ink.
Body modification can be as simple as makeup or as complicated as scarification with a whole lot in between.