Be honest in your statements, questions and answers. If you know what chakras are then you obviously have been reading about them. The site you took the chakra test on should contain basic information about each chakra on it. If it does not then it isn't a reliable test or site. Research the third eye chackra more to find the answer you are looking for. You should be researching all of the chakras and learning how to work with them as well. Chakra work involves all of the chakras since they work in conjunction with each other. You can't strengthen one without working on all of the 7 major chakras together each time you practice. The goal is to open and align the chakras without causing any chakra or chakras to be overactive. I have also listed a link below to a site I recommend for beginning chakra research and practice;
The quick answer to your question is ESP or extra sensory perception, the sixth sense is also another term to describe the third eye's function. Through meditation and utilizing the Kudalini meditation technics you can work on your chakras and experience the benefit to opening and aligning your chakras. To find more information I have also provided another link;
http://www.kundaliniyoga.org/meditation.html
Magically the third eye is used to help with divination and other insight related magical workings.The third eye is also reasonable for one's intuition.
You know most of the chakra tests are fake, ore more like not acurate anyway, but since I have second sight aka the third eye and my third eye chakra was nove where near open when I started developing my third eye aka second sight, the chakra has nothing to do with the ability, in my experience, and some people that I know, but the ability baisicly helps you see the future (soposedly, they categorize it with third sight but there are many other ways and it realy mostly is one of the other ways) but it also lets you see auras, entitys energys and so one and I personaly can see x-ray style and where im not even looking (comes in handy in exams)
