Guided imagery is a story that allows the listener's mind to picture a place where they can be safe. Safe to relax, let the pressures of the day go, a place for their own, A VACATION IN THE MIND! 

It is told with open descriptions so that the listener can picture things as they have either experienced them, heard about them, or seen them.

An example would be: A dog comes toward you. It appears happy. Rather then: A brown Great Dane comes toward you with it's tail wagging. 

The first description allows you to see any dog you want, with wagging tail, bouncing step, drool flying about, ears up or down. The second description only allows you to see the Great Dane and only as described. Which is fine, if you like BIG dogs and if you know what a Great Dane looks like. Not so good if you like small dogs or have never seen a Great Dane