Positive Logic: With reference to positive logic, logical 1 state is the most positive logic or voltage level and logic 0 state is the most negative logic or voltage level. In other words, active high level is 1 and active low level is 0. For instance, V(0) = 0V and V(1) = 5V, V(0) = 5V and V(1) = 15V.
Negative Logic: With reference to negative logic, logic 0 state is the most positive logic or voltage level and logic 1 state is the most negative logic or voltage level. In other words, active high level is 0 and active low level is 1. For instance, V(0) = 5V and V(1) = 0V, V(0) = 15V and V(1) = 5V.
I hope this helps!