Mental imagery is a part of human mentality, the part which allows us to draw pictures within our minds, to create a delicious new recipe, to write a poem, or simply, to daydream. It has played an important role in the evolution and the development of humanity. It still does. It also makes us who we are. .
It is hard to give a definition of the word imagination, because its concept is very wide and abstract. Creation of new ideas is probably the first one that comes to mind. But are imaginative people necessarily also creative? By definition, imagining is creating within our minds, forming mental images or concepts of what is not actually present to the senses (Random House Webster's Dictionary). Every thought, feeling or vision that is not directly a product of sight, sound, smell, taste or touch, i.e. of the present circumstances, is a part of imagination. But if imagination is creation, then knowledge, memories and feelings, which are already ingrained in our minds, cannot or should not be considered as a product of imagination, as they do not involve any creating, only opening a file in our heads. On the other hand, any new concept or idea we think of cannot just come into existence on its own. It must be some kind of combination of our previously acquired knowledge and experience. Therefore, imagination could be defined as formation of mental images and concepts, not present to the senses, formed by combining just about any information our brain has gathered by this point in life.
Be that as it may, imagination plays an important role in the shaping of human mentality. As everything else, this too starts with children. They always have the most vivid imagination, probably because their gray cells are about a hundred times more active than those of an elderly person. Furthermore, their minds are not full of facts and information which form a complete picture of reality, and this enables them to just let go, to let their minds wander off.