Of course you know what you are thinking about right now. Maybe you are thinking about your lunch or the kids or a project you are engaged in. Or maybe you are totally focused on my words right here as you read them.
Even when your mind wanders, you’re more aware of the wandered thought and less aware of the thoughts from which you’ve wandered.
The ability to focus on one train of thought and less on others is called awareness scotoma in which I lock on to one and lock out alternatives. One thought OR another, rather than many.