What is a "fixed" work of authorship in copyright law?

To get copyright protection, you must have a fixed and original work of authorship. To be "fixed," a work must be perceptible for more than a short period of time. For instance, if you are talking with a friend, your statements are not fixed. But if you have the same conversation and record your statements, they are fixed because they are perceptible after the conversation ends, by listening to the recording.