The space between the brows is called the Ajna or the third eye chakra. This is probably the chakra that people are most familiar with, even if you don't know anything about chakras you've heard of the third eye. This chakra is represented by the color indigo and governs our ability to "see" in both the inner and outer world. The third eye is where your wisdom and conscious comes from.
When your third eye is balanced and fucntioning both hempishperes of your brain are functioning properly and you maintain the ability to not only see but also understand things that are happening around you. You intiution is governed here and is important for guiding you through your decision making. A balanced third eye can lead to lucid dreams, visualizations and clairyovance.
An underactive third eye chakra you may have difficulty learning and retaining information. The spiritual world is a mystery to you and you might have difficulty seeing through very simple deceptions. And overactive third eye chakra can cause migraines or mental illness. You may be judgemental, delusional or have some issues deciphering between what is real and what is a fantasy.
Physical symptions of an imbalanced third eye chakra can be insomnia, blindness, deafness, seizures, sinus issues, panic attacks or depression.