What does the expression who are you telling mean?

The expression "Who are you telling?" is a sarcastic way of saying that the person you're talking to already knows something or has experienced something themselves. It implies that you think they are being insincere or pretending not to know.

Here's how it works:

* You're suggesting that the other person is trying to convince you of something that you already know.

* The phrase expresses disbelief or skepticism. It's like saying, "You think I'm going to believe that?" or "Come on, don't try to pull the wool over my eyes."

Example:

* You: "I'm so stressed with my new job. It's so demanding."

* Friend: "I know what you mean, I was so stressed when I started my new job too."

* You: "Who are you telling?" (meaning, you already know how stressful it can be, so don't pretend to understand me.)

In short, "Who are you telling?" expresses a lack of belief or frustration with someone who is attempting to persuade you of something you already know.