How AI Search Engines Work | 1.1. AEO Course by Ahrefs

0:00Hey, it's Ammo and welcome to the first module, which is on how AI search actually works. In this lesson, I'm going to walk you through the three things you need to understand about how AI search engines find, evaluate, and cite content. Because here's the thing, if you don't understand how AI search works under the hood, every optimization tip you hear is just going to feel like a random list of tactics. And I don't want that for you. I want you to understand the why behind every strategy we cover in this course. Let's get started. So, where does AI actually get its information? This is probably the

0:35most important distinction to understand. AI search engines have two sources of information, and they work very differently. The first is training data. This is the massive collection of text that the AI was originally trained on. So, books, websites, PDFs, social media, YouTube transcripts. Basically, a snapshot of the internet. So, when you ask ChatGPT, "Who is the CEO of Apple?" and it instantly says, "Tim Cook" without searching anything, that's coming from training data. It already learned that pattern. But here's the

1:07problem with training data. It's static. It gets updated maybe every 6 months or so. So, if you launched your product last week, the AI doesn't know about it yet, not from training data at least. And that's where the second source comes in, real-time retrieval. This is where RAG, or retrieval-augmented-generation, comes into play. It sounds complicated,

1:27but Patrick Stock said it best. Uh then you've got the the retrieved pages, which is like a secondary process. So, you've got the the trained LLM data, and then you've got the data where it goes out and fetches a bunch of relevant pages, and those come with other probabilities. For example, when ChatGPT or Google's AI mode needs fresh information, or when the question is too specific for training data alone, it goes out. It searches the web using APIs. It pulls back a bunch of pages, reads through them, and then generates a response based on what it found. Now, why does this matter for you? Because it means

2:03there are two ways to influence what AI says about your brand. The first is to be mentioned so widely across the web that you're baked into the training data itself. And second is to make sure your content shows up when the AI searches the web in real time. Guess what? We already know how to do that. That's SEO. The skills you already have from traditional SEO, ranking in Google, earning backlinks, creating quality content, those directly influence whether AI picks up your pages during real-time retrieval. Now, here's where it gets interesting. The AI doesn't just

2:36search for the exact thing you typed in. Let me explain. Search engines used to work one-to-one. One query, one set of results. Then they evolved to many-to-one, where different queries like Sydney plumber and plumbing service in Sydney could return the same results. But AI search has flipped the model to one-to-many. One search gets expanded into many. And

3:00this technique is called query fanout. For example, when someone enters a prompt like plan me a 5-day trip to Japan in November, the AI fans it out into dozens of smaller long-tail subqueries. Things like best neighborhoods to stay in Tokyo, November weather in Kyoto, Japan Rail Pass worth it, all running simultaneously behind the scenes. It then pulls information from multiple sources across the web and combines it into one complete answer. In fact, research from Seer Interactive in Nectaf found that the average prompt triggers nine to 11 fanout queries, with some going as high as 28. And ChatGPT's deep research mode ran 420 searches for a single query about buying a red phone

3:45case. So, if your content ranks for those niche specific queries, your brand has a much better chance of being included in the AI's final response. And this is a huge shift from traditional SEO, where you could optimize one page for one target keyword and call it a day. In AI search, you need to be relevant across an entire topic, and I

4:07could even argue across an entire niche. Because if your page about how to start a podcast only covers the basics, but doesn't mention equipment, hosting, or promotion, the AI is going to find someone else's page that does. Now, you might be wondering, "Can I see these fanout queries?" You sure can. In the AI responses report in Ahrefs Brand Radar, you can see the fanout queries for ChatGPT and Perplexity prompts. But there's an important caveat. Justyna from Ahrefs wrote in her guide on query fanout that these aren't like traditional long-tail queries. They're synthetic, generated by AI in the moment. They're inconsistent. The same prompt can trigger different fanouts

4:51every time. And over 95% of them have zero search volume because real humans would never type them. So, don't think of fanout queries as a new keyword list to optimize for. Think of them as a window into what topics the AI considers important for a given question. We'll get into exactly how to use this strategically in module two. Because for now, we need to talk about how AI decides who to actually cite. In traditional search, rankings are relatively stable. Like, if you're number three for a keyword today, you're probably going to be somewhere around there tomorrow. But AI citations are probabilistic. Patrick Stocks explained this really well. He said, "AI outputs

5:32are built on probabilities on top of probabilities on top of probabilities. The training data creates patterns that retrieve pages add their own signals, and then there's a temperature setting that introduces randomness so the AI doesn't generate the exact same answer every time. Now, what that means in practice is that if you ask the same question five times, you might get cited three out of five, or the AI might mention your competitor twice, and you twice, and someone else once. There's no fixed position to rank for. This is why we talk about AI visibility rather than AI rankings. It's more like a probability distribution than a leaderboard. Now, that said, there are

6:13patterns in what gets cited more often. Based on the data we've studied at Ahrefs, consensus matters. If multiple sources on the web say the same thing about your brand, AI is more likely to repeat it. And the more places your brand is mentioned in a consistent way, the higher the probability the AI picks it up. Freshness matters. AI-cited content tends to be about 25% fresher than what you'd see in a traditional serp. The AI is actively looking for recent information, especially for topics that change. Authority still matters. Pages that rank well in traditional search have a major head start. Our data shows that 76% of AI

6:52overview citations come from pages already in the top 10 of Google. So, I'll hit that gong one more time. SEO is the foundation of AEO, but it's not only about Google rankings. 14% of pages cited in AI overviews don't rank in Google's top 100 at all. And for platforms like ChatGPT, the overlap with Google's results is even lower. So, there's real opportunity for brands that aren't dominant in traditional search to still show up in AI. So, let's tie all of this together. AI search engines pull from training data and real-time web search. They expand your one query into

7:31dozens of subqueries through fanout. They merge and score results from all of those searches, and then they generate a response that's probabilistic, not fixed, based on patterns, consensus, freshness, and authority. Understanding this process is what makes every other lesson in this course make sense. So, when I tell you to earn more brand mentions, it's because of how consensus drives probability. When I talk about topic coverage, it's because of query fanout. When I say that SEO is the foundation, again, it's because 76% of citations come from pages already ranking well. Now that you understand the mechanics, the obvious next question is, do all AI platforms work the same

8:14way? And the answer is not even close. Not even close. In the next lesson, we're going to compare AI overviews, ChatGPT, Perplexity, and Google's AI mode side-by-side. And the data on how different they are is pretty surprising. I'll see you in the next lesson.