difference between c/k and r

[hurtsme2]

excuse the what may seem to others as a stupid question. I'm new to these I have a 87 r10 silverado. When I'm searching for parts in this case "add a leaf springs" I'm seeing c/k springs but not r what are the differences.

I have alot of questions to ask and from reading for the last week there are a lot of good people here. I will be posting photos of my body off frame up restoration.

thanks