I've just gotten into Dark Horse's reprints of Savage Sword of Conan. I love it, it's great. But then there's this Conan the Barbarian series also from Marvel in the 70's. Here's where I'm confused, I thought they were completely different series but as I flipped through a copy of Conan the Barbarian reprints in Chronicles of Conan series by Dark Horse I recognized several issues as already being in Savage Sword of Conan Vol. 1 which I have. Are they separate series or what? I don't get it!

Marvel would sometimes print censured (but colored) versions of the Savage Sword (SS) stories in the main Conan the Barbarian (CtB) series. An example can be seen here. SS would also sometimes re-adapt Robert E. Howard stories that already been done for CtB, but these are all-new adaptions. The Chronicles of Conan vol. 4 also collects the Red Nails story from SS #2-3 among the CtB reprints for whatever reason.