Researchers found that a nap reboots the brain, improving learning and memory. Of course, expert nappers like myself reject the notion that napping needs a purpose.
My 4th Commandment of Napping says:
(4) Don't over-analyze. As noted in my "The Tao of napping," researchers have found proven health benefits to taking a nap. But a nap doesn't need justifying. It is what it is.