Words can be chosen to create more than just meaning: they create feeling, too. Some words (or phrases) are able to create a particularly vivid sense such as a picture, a sound, a taste, etc. This effect is called imagery.
Imagery is a very important feature of descriptive writing and, especially, of poetry. The most common way by which a writer can create imagery is through the use of figurative language, typically through the use of metaphor, simile and personification.
Truly effective imagery acts almost to etch itself onto the reader's mind. This can be a very emotional and persuasive device as it acts to engage the reader intensely in the subject matter of the writing.