The telephone nurse is typically an employee of your health insurance company. She may work 24 hours, or extended hours, and you can call her up from your sick bed to whisper your fears about genital warts or have her assure you that a tickle in your throat is not always pneumonia.
Her role is to screen out the hypochondriacs, leave them with good advice and maybe a little solace, prevent them from unnecessarily running to the doctor and costing the insurance company money. But if you've called the telephone nurse, you may have gotten the impression that she's the only person employed by your insurance company who gives a fuck about you (but let's not get me started).
Personally, I can't count the times the telephone nurse has saved my worry-prone bacon. For instance, the time I gave myself chemical burns with an overenthusiastic application of depilatory goop (solution: no matter what the box says, wash it off with soap and warm water). Or the time when, after making a career of faking it to get out of PE in school, I genuinely did have the stomach flu but was convinced it was cancer (solution: if you still can't keep food down after a week, see the doctor).
If your health insurance plan doesn't have one, your employer clearly hates you and wants you to quit. If you're not one of the twelve people in the United States who has health insurance, you're missing out!