what are you talking about
Tom no entiende de qué estás hablando.
Tom doesn't understand what you're talking about.
Tom ni siquiera sabe de qué estás hablando.
Tom doesn't even know what you're talking about.
Sé exactamente de qué estás hablando.
I know exactly what you're talking about.
Tú mismo no sabes de qué estás hablando.
You don't even know what you're talking about.