In plain terms
You search, and before the familiar list of links Google shows a few paragraphs written by its AI that answer your question, with small links to the pages it used. For many questions the user reads that and stops. The page that would once have received the click may now be a small source link, or absent.
Why it matters
For most companies Google is still the largest source of discovery, and this feature changes what a top ranking is worth. Informational pages are the most exposed: several industry studies report noticeably lower click-through when a summary is shown. Traffic reports need rereading with that in mind, and content strategy shifts toward being a cited source and toward pages people need to visit, such as tools, data and products.
Example
A health-information publisher sees visits to its “what is…” articles fall while its search positions hold steady. The pages still rank; the answers are now read on Google. It moves investment toward calculators, original research and in-depth guides that a summary cannot replace, and tracks how often it is cited in the summaries.
Most often confused with
AI Overviews vs. Featured snippet
A featured snippet lifts a passage verbatim from a single page and links to it. An AI Overview is composed by a model that synthesises several sources into new text, with the sources shown as supporting links. Losing a snippet meant a competitor's passage was chosen; with an overview, no single page “wins” the answer.
Origin: Launched in the United States in May 2024, following the Search Generative Experience experiment of 2023, and since extended to many countries and languages.
Under the hood
Generated by Google's Gemini models on top of the search index. Google describes a “query fan-out” technique in which the system issues several related searches and combines the results. Whether an overview appears depends on the query; they are most common for informational questions and rarer for navigational or transactional ones. There is no special markup for inclusion: eligibility follows from being indexed and eligible for a snippet, and publishers can limit use with snippet controls such as nosnippet and max-snippet. Search Console counts overview impressions and clicks within overall search performance, which makes their separate effect hard to isolate. AI Mode is a related, conversational Google search experience.