Mostly, nothing. These are five names for substantially the same work, coined by different people at different moments, each hoping their label sticks. I'd put the overlap at roughly nine parts in ten. The differences that remain are matters of scope and emphasis, not of method — and no one selling you one of these acronyms will tell you that, because the acronym is the product.
Here's each one, honestly, including the one I use.
AIO — AI Optimization
The broadest of the terms, and the one I use. It covers everything involved in getting AI systems to understand, trust, and cite your business — whether that system is a chat assistant, an AI overview inside a traditional search page, or something that hasn't shipped yet.
I prefer it precisely because it doesn't bet on a technology. "Generative," "answer engine," and "large language model" all name a mechanism, and mechanisms get replaced. "AI" names the category. When the current architecture is superseded — and it will be — the label still fits.
GEO — Generative Engine Optimization
The most widely used alternative, and the one with the most academic weight behind it — it came out of published research rather than a marketing department, which is more than most of these can claim.
It means optimizing to be cited by generative systems: ChatGPT, Gemini, Perplexity, AI overviews. In practice that is what I've described on this page. If you've been reading about GEO and landed here, you're in the right place. The one real distinction is that GEO points specifically at generative systems, where AIO also covers AI-driven retrieval and ranking that never generates prose at all.
AEO — Answer Engine Optimization
The oldest of the group, and the only one with a genuinely separate history. AEO predates the current AI wave. It grew up around featured snippets, People Also Ask boxes, and voice assistants — the zero-click era, when Google started answering questions on the results page instead of sending you somewhere.
That history gives it real content. The discipline of writing a crisp, extractable, direct answer was developed for snippets and voice, and it transfers almost perfectly to AI citation. If you optimized for featured snippets years ago, you were doing proto-AIO without knowing it. Today most people use AEO and GEO interchangeably, which slightly buries the useful distinction.
LLMO — Large Language Model Optimization
Sometimes written LLMSEO. It names the underlying technology rather than the user's experience, which tells you it was coined by engineers rather than marketers.
Its problem is that it's already narrowing. The systems your customers use aren't bare language models — they're models wired to search indexes, retrieval layers, and live tools. The retrieval half is often what decides whether you get cited at all, and "LLM optimization" doesn't describe that half. I'd expect this one to fade.
GAIO — Generative AI Optimization
GEO and AIO welded together. It carries no meaning that GEO doesn't already carry, and it has the least usage of the five. I mention it here only so that anyone who arrived searching for it finds a straight answer instead of a sales page.
My honest read: this one doesn't survive.
And SEO?
Still the parent discipline, and still most of the work. Every one of these acronyms describes a specialization within SEO, not a successor to it. A fast, clean, credible, well-structured site is the prerequisite for all of them. Anyone presenting AIO as SEO's replacement is either confused or counting on you being new here.
So which should you care about? None of them, really — care about the work. Every term above resolves to the same instruction: publish genuinely useful, genuinely expert, clearly structured information that a machine can read and a person can trust. Optimize for that and you are simultaneously doing AIO, GEO, AEO, and LLMO, whatever the winning label turns out to be.
I chose AIO because it's the most durable and the least likely to embarrass me in three years. But if you call it GEO, I'm not going to correct you. We'd be talking about the same thing, and I'd rather spend the hour on your website than on your vocabulary.
Will Your Law Firm Show Up When Someone Asks AI for an Attorney? Ranking in Google Is No Longer Enough
