Answer engine optimisation focuses on being the extracted answer to a specific question. Generative engine optimisation focuses on being cited as a source inside a synthesised response. AEO targets extraction; GEO targets attribution within generation.
In practice the technical work overlaps substantially — both depend on extractable, corroborated, retrievable content.
The distinction matters most for measurement: extraction and citation are different observable events.
Treat vendors using the terms interchangeably with mild caution.