This sensation is normal during meditation and the place is called Ajna (or third-eye chakra - the mind's eye). In statues of buddhas it's placed on the forehead as a most previous jewel.
In Tibetan buddhism, this chakra is at the end of the central channel, which runs up the body to the top of the head, and then over and down, terminating at the forehead. The two side channels continue onwards towards the two nostrils and end there. [Source: wiki]
From a spiritual point of view, we could compare the third eye to the temple's portal to the sacred places or the bridge allowing mind communication.
The purpose of meditation is to reveal this natural subtle perception (vibrating sensation). The best results are achieved when you don't use your imagination/visualisation, so things will come to you naturally (just flow with what comes). So if you feel vibration (or pressure, density) between the eyebrows, don't pay attention to it, just focus on the vibration and try to connect this energy with your throat chakra (Vishuddha) in order to create the circulation of the life force (Lung/Qi/Vijñāna), so you can sense your light/astral/etheric body.