Each humbucker has two coils in it. For "Outside Coils" your sitches connect one coil from the neck pickup (nearest to the neck), and one coil from the bridge pickup (nearset to the bridge). This pair of coils is located 'outside' of the pair that is not used.

"Series" means that the coils are connected so that there is only one path for current flow - through one, and then the other.
____(pup)____(pup)____

"Parallel" means that the ends of the coils are tied together so that there are two (parallel) paths for current flow.
. ____(pup)______
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