1. Imagery is any literary reference to the five senses (sight, touch, smell, hearing, and taste). Essentially, imagery is any words that create a picture in your head. Such images can be created by using figures of speech such as similes, metaphors, personification, and assonance. Imagery helps to create a strong sense of mood in a work.
2. Imagery is also the term used to refer to the creation (or re-creation) of any experience in the mind – auditory, visual, tactile, olfactory, gustatory, kinesthetic, organic. It is a cognitive process employed by most, if not all, humans. When thinking about a previous or upcoming event, people commonly use imagery. For example, one may ask, "What color are your living room walls?" The answer to this question is commonly retrieved by using imagery (i.e., by a person mentally "seeing" one's living room walls).
3. Remembered imagery is mostly based on what an individual has already experienced. People have a clear image of those "experienced" things, which they can recall at will.
4. Imaginary imagery does not seem to have a corresponding equivalent in the real world -- often it is a strange combination of remembered images, or of remembered images mixed with confabulation. Imagery can also be based on what has not been experienced. In this case, it is commonly used to 'fill in the gaps' in one's mind. A common example of this is a child having nightmares of a monster when the room is dark. They can 'imagine' a monster coming out of nowhere to attack them. Imagery is often used by poets and author to help the reader imagine what is happening and helps the reader to become absorbed in the article/book and allows the reader to see what is in the author's mind.