US politician Donald Rumsfeld actually popularized this one back in 2002 when he answered a reporters questions like this
There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don’t know. But there are also unknown unknowns. There are things we don’t know we don’t know.
I’m steering clear of the politics related
to the message, let’s just crystalize the mental model which includes three main components:
1. Known Knowns
Things we are aware of and understand. In other words knowledge that’s we’ve identified we have.
2. Known Unknowns
Things we are aware of but do not understand. Or gaps in our knowledge that we’ve identified we have.
3. Unknown Unknowns
Things we are neither aware of nor understand. These are the blindspots we have - we haven’t identified the knowledge we don’t have.