Symlink / hardlinks in English (vastly simplified)
Imagine a file named "x" that requires 100Meg to store.
Such and such program wants to store a copy of that file under the filename "y"
Without symlinks / hardlinks, the copy would take up another 100Meg. With links, the copy doesn't take up any extra space, as the "y" filename simply points to the exact same data that "x" does.
Plex makes very extensive use of them, and any backup of Plex's appdata without handling symlinks / hardlinks is pointless. Either add the switches, or use CA's appdata backup.