Trance is a state of consciousness that is experienced regularly by everybody, for example during sports, when you daydream on the train, whilst you are busy in the kitchen pealing peas, during meditation,….. Our brain operates on very fast beta waves during our daily conscious activities. When you relax from normal brain activity, and move into trance, those frequencies will reduce to alfa (mental relaxation, meditation) and theta (creativity, dreams, expanded awareness).
We absorb an enormous amount of information through our senses. From that only a small part of that will be consciously processed by the brain. In trance you can get in touch with the information which has been absorbed subconsciously. You will see connections which you did not previously see, and you might look at things from a different perspective. Like in dreams, in trance you process things and clean up your system, like you would on a computer, when every now and again you empty your trash can, or deframent your hard disk.
Read more about trance and consciousness here: