The K in Chevy Trucks indicates that the Chevy Truck is a 4 wheel drive truck.
When the Chevy Truck has a C in it the C means that the Chevy Truck is a 2 wheel drive truck.
So a C 1500 Chevy Truck will be a 2 wheel drive truck while a K1500 Chevy Truck would be a 4 wheel drive truck.
I wondered the same myself until I asked a mechanic a few years ago and he told me what the K and C meant on vehicles.
I knew when I saw a 4 wheel drive or 2 wheel drive truck but I was unsure at the time what the C and K stood for on the trucks.
But after asking the mechanic about it I found out.