These feed into the areas of your brain that interpret that environment. Imagery seeks to create a similar set of nerve impulses that can feed into those areas of the brain that experience the outside world. You can bring all your senses into the image, with sounds of running water and birds, the smell of lavender, the taste of cool spring water, the warmth of the sun, etc. Use the imagined place as a retreat from stress and pressure. Your image can be anything that works for you, as long as it feels peaceful.
Scenes can involve complex images such as lying on a beach in a deserted cove.
It allows you to practice in advance for anything unusual that might occur, so that you are prepared and already practiced in handling it. This helps to give you the self-confidence you need to do something well. Many athletes and performers use this method. Recently, this writer heard a professional golfer admit that he imagined himself playing a particular hole in a tournament before he actually played. In his mind he envisioned the ball going into the hole even before he putted.