What is Google Gemini?

Gemini is a name Google uses for several things at once, and it pays to separate them before deciding anything: the AI models, the app that puts them on your phone and the part of Search that writes answers. We are not talking about the zodiac sign or the cryptocurrency platform of the same name. For a store it matters because Gemini is both an assistant people ask what to buy and the engine behind Google's AI search, and each of those two faces reaches your site by a different route, with different controls.

What it includes

The models. Google introduced Gemini on December 6, 2023, in a post signed by Sundar Pichai and Demis Hassabis, as a model that is multimodal from the ground up: it understands and combines text, code, audio, image and video. The first version came in three sizes: Ultra, for the most complex tasks; Pro, for a wide range of uses, and Nano, for running on a device. Bard then got a tuned version of Gemini Pro, and the Pixel 8 Pro was the first phone with Gemini Nano.⁠^{[1]Google, official blog (Sundar Pichai and Demis Hassabis, December 6, 2023). Introducing Gemini: Google’s most capable AI model yet} It is an LLM (large language model), the part that writes, with the added ability to read images and sound.

The assistant. On February 8, 2024, Google announced that Bard was being renamed Gemini, with a new app on Android and inside the Google app on iOS.⁠^{[2]Google, official blog (February 8, 2024). Google Bard is now Gemini: How to try Ultra 1.0 and new mobile app} When it answers, the Gemini app can link sources and related content: public websites, files you have uploaded or, if you have connected it, Google Workspace documents and email. The sources button appears at the end of the answer or throughout the text, and Google warns that not all responses include links or sources.⁠^{[3]Gemini Apps Help. View related sources from Gemini Apps}

The search engine. When Google launched AI Overviews for all of the United States, on May 14, 2024, it explained that a Gemini model customized for Google Search made it possible.⁠^{[4]Google, official blog (May 14, 2024). Google I/O 2024: New generative AI experiences in Search} AI Mode also answers with Gemini models: Google brought a custom version of Gemini 2.5 into Search for both AI Mode and AI Overviews in the U.S., and AI Mode breaks the question into subtopics and issues a multitude of queries simultaneously,⁠^{[5]Google, official blog (May 20, 2025). AI in Search: Going beyond information to intelligence} which is called query fan-out.

Shopping. On January 11, 2026, Google announced that the UCP (Universal Commerce Protocol) would let people check out on eligible product listings in AI Mode and the Gemini app, from participating merchants, starting in the United States and with plans to expand to other countries. Stores turn it on from Google Merchant Center.⁠^{[6]Google, official blog (January 11, 2026). New tech and tools for retailers to succeed in an agentic shopping era} On May 20, 2026 it added a universal cart that works in Search, in Gemini and in Maps, with Google Pay checkout, for Australia, Canada, India, New Zealand and the United States, and the United Kingdom later.⁠^{[7]Google, official blog (May 20, 2026). Google helps retailers thrive with new UCP and AI tools}

How it reaches your store

By two routes, and each has its own control.

The Search route. To appear as a link in AI Overviews or AI Mode, a page has to be indexed and eligible to be shown in Search with a snippet; there are no additional technical requirements. What is shown from your pages is limited with the usual controls: nosnippet, data-nosnippet, max-snippet or noindex.⁠^{[8]Google Search Central. AI features and your website}

The models and app route. Google-Extended is a standalone identifier, separate from the crawlers, used in robots.txt to decide whether what Google crawls on your site can be used to train future generations of Gemini models and for grounding, that is, to base the answers of the Gemini apps and of the Grounding with Google Search service in Vertex AI on your pages. Google makes clear that Google-Extended does not affect your site's inclusion in Search and is not a ranking signal.⁠^{[9]Google for Developers. Google's common crawlers}

In a store

A store that sells in the United States and wants to know where it can show up in Gemini, and what it decides, has this map:

The table shows what gets confused most: the first two rows look like the same thing and have different controls. Blocking Google-Extended touches the app and training; for AI Overviews and AI Mode, the control is in indexing and snippets. To know what Gemini says about your products you have to ask it: Clione, for example, asks ChatGPT and Gemini the questions shoppers ask and shows whether they name the store's products and who takes their place when they do not.

How to check it

1. Open your robots.txt and look for Google-Extended. If it appears with a Disallow, you have decided your content will not train Gemini models or ground the app's answers; your presence in Search does not change.⁠^{[9]Google for Developers. Google's common crawlers}
2. Confirm your product pages are indexed and allow a snippet, which is what AI Overviews and AI Mode ask for in order to link to you.⁠^{[8]Google Search Central. AI features and your website}
3. Ask the Gemini app what a shopper would ask and open the answer's sources, if there are any. Repeat on another day: one answer is a sample of one.⁠^{[3]Gemini Apps Help. View related sources from Gemini Apps}
4. If you sell in the United States or another country on the list, check Merchant Center, which is where UCP checkout is turned on.⁠^{[6]Google, official blog (January 11, 2026). New tech and tools for retailers to succeed in an agentic shopping era}⁠^{[7]Google, official blog (May 20, 2026). Google helps retailers thrive with new UCP and AI tools}

Related concept: Google AI Mode

Google AI Mode is a Search feature that answers with Gemini models;⁠^{[5]Google, official blog (May 20, 2025). AI in Search: Going beyond information to intelligence} the Gemini app is a separate assistant. The practical difference is in the route: AI Mode links pages from the Search index that can be shown with a snippet,⁠^{[8]Google Search Central. AI features and your website} and the app can draw on public websites, your files or your email, with Google-Extended as the control for use of your site.⁠^{[3]Gemini Apps Help. View related sources from Gemini Apps}⁠^{[9]Google for Developers. Google's common crawlers} Same model, two products, two switches. Its Microsoft counterpart is Copilot.

To go further, the AI search reading path orders the rest of the terms, and the entry on AI Overviews explains the other Search feature that writes with Gemini.