Figurative speech describes a way of using words to convey meaning without directly stating the message being conveyed. Figurative speech may be spoken or written. Figures of speech are used to make communication more interesting or to add emphasis, but can lead to problems when the receiver of the communication doesn't understand the meaning being implied by the figure of speech.
For example, someone wanting to report that it is raining very hard might say, "It's raining cats and dogs." This figure of speech is intended to express the idea that lots of large raindrops are falling from the sky, not that literally cats and dogs are falling from heaven.
Another example - when you are looking forward to some future event, you might say, "I can't wait for it to happen!" In actuality, you have no choice but to wait - but this conveys that you are anxious for the beginning time to arrive.