BIM Server Libraries. Copies of our standard libraries for use in Teamwork projects.
Library Container Files. An LCF is a compressed archive of a library. It loads very fast and can't be messed up, so it's good for taking projects on the road assuming you don't need to modify standard parts. I try to update the LCF of our current versions' library (13 and 16 at the moment) on a weekly basis. But I might forget, and I certainly modify objects throughout the week, so if you need the LCF you should make sure it's up to date.
Master LIB [n]. Where n is between 7 and 20. The Master folder contains the current "1 Rill LIB[n]" folder, which is standard library that must be loaded for all current projects. It also contains a "Development" folder, which should generally not be loaded; things in there are either broken, unfinished, or otherwise unworthy.
When we start using a new version of Archicad, I copy the entire Master LIB folder and give it the new number. When you switch a project to a new version, you should also change to the newer Master LIB. It will be virtually identical to begin with, but over time the old versions will fall behind. I generally only treat the newest Master LIB as "live" for the purposes of new development and bug-fixing. Back-saving objects, unlike PLN files, is nearly prohibitive in its awkwardness.
Other LIBs. Just what it says. Old project libraries from the pre-embedded days. Old Archicad libraries. (I've lost the 5.1, but we still have the 6.0.) Extracted versions of recent/current Archicad libraries. (Archicad libraries are LCF files. If you want to search them using the Finder, they need to be extracted.)