Global vs local means to which context inside of kicad something is added not where on the filesystem (kicad does not care where you put libs it only cares how you add them to kicads setup)
See: Library management in KiCad version 5
When creating a new library you are not only asked if you want to place it into the global or local context but also for a file system location.
- Creating a new symbol library and a new symbol in KiCad 5
- Creating a new footprint library (for version 5.0 and earlier. 5.1.x works the same as the symbol side so look at that for information.)