CodeAurora (CAF) - These are Qualcomm's reference sources for their platform. This is what they provide to OEMs, and what nearly all OEMs base their software off of. As a result - nearly all non-Nexus devices are running kernels/display HALs/etc. that are derived from a CAF baseline.
Google's software baseline, or AOSP - Usually when Google starts working on a new Android version, they'll fork from CAF at the beginning. Very often Google will be adding "new" features specific to the new Android version, while Qualcomm will continue with performance enhancements and bugfixes against the "old" baseline.
So when a new Android revision comes out, you have two baselines: CAF which is usually "ahead" in performance but "behind" in features, and AOSP which is the opposite.