What's the difference between AEO, AIO, and GEO?

Less than the marketing implies. There's no agreed industry standard separating the three, and most agencies use them interchangeably — one firm's GEO package is another's AEO package. Judge any pitch on the scope of work, not the acronym on the invoice.

The labels are still useful if you treat them as three jobs rather than three products. AEO — answer engine optimization — is the content layer: pages built so an assistant can lift your answer cleanly. AIO — AI optimization — is the machine-readable layer: schema, entity consistency, large language model instructions, and crawler access. GEO — generative engine optimization — is the authority layer: earning the third-party citations models draw on when deciding whose name to say.

They aren't three retainers, because doing one without the others fails in a different way each time. Answer content a model can't parse never gets quoted; flawless markup with nothing worth citing gets read and ignored; authority with no extractable answers gets summarized around you.