An author can use descriptive words to have their readers visualize what they are trying to portray. For instance, by saying, "Tom ate a red apple." Your mind subconsciously sees someone eating a red apple. However, usually the author will be more subtle. In "To Kill A Mockingbird", the character 'Boo Radleys' home was described as have "rain rotted shutters", "off white", and "low, sinking to the ground with it's old age." This description shows you what his home was like, and creates an atmosphere of suspicion and maybe even fear.
