I know what you are
What you say when you have no idea what someone is talking about. It's like pretending you're smart but you're really just confused.
'I know what you are,' he said, like he knew everything and I was clueless.
She said it like it was a big deal, but I had no idea what she was talking about.
He texted me, 'I know what you are,' like he was the only one who understood.