It is basically tattooing of colors on your face. Be very careful because those people dont have to same training that tattoo artist are required to have...normally they only take a three day training session and off they go on some poor person who doesnt know.
You can research it online or at your local library to find out more. If you do decide to go through with i find someone who has had at least more than three days of training for it. Also make sure the place is clean and safe.