full time 4x4 ??

[us111]

HI all,,i have a couple questions i'm sure everyone but myself can answer..lol..anyhow i have had 4wd before just never got into the working of them,,now i have a 1976 k-10,shortbed,4x4 ,camper special is what it is listed as that i am restoring so i figured it was time to learn about 4x4..as i said i have been told it is full time 4wd,,what does that mean exactly??? also the shift pattern tag on sunvisor is all faded out,,i can make out just enough to make it confusing and thought i would ask you all just exactly what all this is?? i do not know what transfer case it has but it all appear's original and is mounted to a th350 tranny...i just wanna learn before i go tearing gears out or something ...thank you all for any help you can give....(more the better)..