PESOS is an acronym for Publish Elsewhere, Syndicate (to your) Own Site. It’s a syndication model where publishing starts by posting to a 3rd party service, then using infrastructure (e.g. feeds, Micropub, webhooks) to create an archive copy on your site.

The opposite (and preferable) approach is POSSE, whereby a user publishes original content to their own site, and then syndicates copies to 3rd party services, preferably with perma(short)links back to the originals on their own site.

PESOS, IndieWeb, https://indieweb.org/PESOS