Imagination is our ability to create new mental images, and is involved in the search and construction of knowledge in all areas.
Why is it vital?
It is available to all humans, regardless of their culture, religion, linguistic and socio-economic background, time, and place they live in. It plays an important role in all creations and representations, and has no limitations therefore encouraging evolution.
The mind's eye
A phrase that describes the creation of imagined or recollected mental images that can be made up of any sensory input (most commonly visual). For example, whilst reading a book you come across a scene set in a field. Your mental images will be composed of a field you have been in or seen in a picture, and perhaps even fill in the gaps (if any) without resorting to a past experience. This second step is more challenging.
A neurological perspective
Our neurons work together in a neuronal ensemble to construct mental images when thinking creatively. Neurons in the prefrontal cortex fire and carry electrical signals of characteristics of an object, and when trying to imagine the object again, the same neurons will fire. On the other hand, mental synthesis happens consciously when trying to imagine something we have not seen. The prefrontal cortex combines other stored images to create a new image. This ability is said to be unique to humans.
Imagination VS creativity
Creativity is the ability to to join together distinctive ideas in new and useful combinations. It could be said that these two concepts are interdependent or that creativity relies on imagination. Others say they are distinctive, with creativity being purposeful and producing useful ideas, and imagination lacking purpose or leading anywhere.
Mental rehearsal/motor imagery is a technique often used in sports in which imagery is used to mentally rehearse a given action.