Thoughts and meditation.
Not "discarded" no. Just not touched. That's why they said leave front and back doors open. So they can enter and exit. You don't have to chase them away.

But yeah, some thoughts can be very cool and interesting. And the more you meditate, more interesting they get :)
It is very tempting to think about some of them...

It doesn't mean you should stop them or not stop them, or be guilty, or proud. Just remain open and don't serve tea to the thoughts, I love that expression.