I found it fascinating in jr high math class that someone had to “discover” zero and negative numbers for discovery in mathematics to really explode.
Those are concepts.
My 6 & 8 yr old understand negative numbers because of an analogy to something they’re familiar with.
I used legos. Stack legos 1,2,3,4 high... Now, envision digging a hole in the floor that requires you to put 2 legos in to get to floor level. That’s -2.