Why did i get Truck B plates?

[Octavio]

I have 2 chevy colorado,
one has letters on the plates and a space in the middle, and my most recent purchase they gave me "Truck B" plates, why? whats the difrence? both same year exept the one with b plates is a cheap base model, whats the advanteges or disadvanteges? i do know that now i cant go onto lake shore drive,

i live in illinois if it helps