A peiron (derived from the Greek word for 'limited' or 'continent') is just an alternative name for a single 'region' (more acceptable name), which is, by default, separated from other regions by an indefinite, unpredictable and incalculable area of sea, which has no lifeforms inhabiting this area of ocean and the seabed is made of rocks whose patterns are randomly generated by an algorithm. All that happens in this body of water, or 'inter-regional waters' as it is known ICly, is that you transport your troops or send your nukes across.
Peirons can not be mutually fixed to relative distance or direction, doing so will technically make them one single peiron and the inter-peiral waters are replaced with just a generic, large, but real body of water. Megapeirons are used as a term sometimes.
Peirons/regions are not necessarily connected to the gameside regions, not everyone who resides in a region gameside-wise becomes part of the peiron in-character. Peirons also do not possess any 'constitutive threshold', any island, or collection of islands, or landmass, or collection of landmasses that have a distinct presence can count.
'Heptapeirons' are peirons that use RL geography (seven continents, from which the badly translated pseudo greek name comes from). No matter how original your cultures are, so long they're on an RL map, they're heptapeiral geographically.
thanks to original person that had the ideas of this concept because i lack any creativity; the oceans part of this is merely a compilation and reorganization of previously widely practiced unspoken rules in RP.