SERP API & AI Search Glossary (2026): 25+ Terms Defined

Search changed faster than its vocabulary in 2026. Between classic SERP features and the new wave of AI answers, the field is full of overlapping terms — AI Overview vs AI Mode, AEO vs GEO, grounding vs RAG, rank vs pixel position. This is a single, plain-English reference for all of it: 30 SERP API and AI search terms, grouped by theme, each with a one-paragraph definition and a link to a deeper guide when you want more. Bookmark it and jump in.

Search results & SERP features

Organic Result

A standard, unpaid search listing ranked by the engine’s algorithm — the classic “blue link” with a title, URL and snippet. Organic results are what most rank tracking measures, and what a SERP API returns first.

SERP Feature

Any element on a results page beyond the plain organic links: the AI Overview, featured snippet, People Also Ask, local pack, knowledge panel, image and video carousels, and more. Parsing these reliably is most of what a SERP API does — see parsing Google SERP features in Python.

Featured Snippet (Position Zero)

A boxed answer Google lifts from a page and shows above the organic results, often called “position zero.” Winning it can capture the click even when you don’t rank first — our guide to featured snippets covers how.

People Also Ask (PAA)

An expandable list of related questions on the results page, each revealing a short answer when clicked. PAA is a goldmine for content ideas and question targeting — you can mine it (and autocomplete) as a free AnswerThePublic alternative.

Knowledge Panel

An information box, usually on the right of the results, summarising an entity — a person, company or place — from Google’s Knowledge Graph. It is a structured SERP feature you can extract alongside the rest of the page.

Local Pack

The map plus a short list of local business listings shown for queries with local intent (“plumber near me”). Tracking it is the heart of local SEO rank tracking.

Pixel Position

How far down the page, in pixels, a result actually appears — as opposed to its ordinal rank. With ads and SERP features pushing results down, pixel position is often a truer visibility signal. We explain it in what is pixel position.

Autocomplete

The query suggestions an engine shows as you type, drawn from real searches — a rich source of natural phrasing for keyword research. Here’s how to scrape Google autocomplete for free.

num=100

A Google URL parameter that once returned 100 results in a single request. Google removed it in September 2025, so covering the top 100 now takes about ten paginated calls — which multiplied deep-rank tracking costs on per-page providers.

AI search & answer engines

AI Overview (AIO)

Google’s AI-generated answer shown above the organic results, citing a handful of source URLs. Being one of those sources is the new prize — you can extract AI Overviews at scale to track it.

AI Mode

Google’s fully conversational AI search experience, separate from the AI Overview block and driven by its own ranking factors. Its citations barely overlap with the AI Overview’s.

Query Fan-Out

The technique where an AI search system issues several related sub-queries behind one user question and synthesises an answer from all of them. It explains why citations increasingly come from pages that don’t rank for the original term — decoded in query fan-out explained.

Citation

A source link an AI answer attributes its information to — the AI-era equivalent of an organic ranking. Understanding how AI search engines choose which sites to cite is now core to visibility.

Grounding

Supplying a language model with external, retrieved facts — such as live search results — at query time, so its answer reflects current sources rather than only training data. It is the idea behind most accurate AI search; see reducing LLM grounding cost.

RAG (Retrieval-Augmented Generation)

An architecture that retrieves relevant documents and feeds them to a language model as context before it generates an answer. A SERP API is a common retrieval layer — see real-time RAG with search.

The Great Decoupling

The widening split between search impressions and clicks as AI answers satisfy users on the results page without a visit. We show how to measure the resulting traffic loss.

AI Visibility

How often and how prominently a brand appears in answers from AI search engines and assistants. The metric behind it is covered in AI visibility scoring explained, and the tools in our comparison of AI visibility tools.

AI Rank Tracking

Monitoring whether and where a brand is cited across AI assistants — Claude, ChatGPT, Gemini and Perplexity. Serpent API’s AI Ranking API is built for exactly this.

Share of Voice

A brand’s portion of total mentions or citations across a set of tracked queries, relative to competitors. Build a cross-engine version in our AI share of voice tracker.

Optimization disciplines

SEO (Search Engine Optimization)

Optimising content and sites to rank in classic search engine results. Still foundational — and still the best predictor of being cited in AI answers, per the data in our AI Overview citations vs rankings study.

AEO (Answer Engine Optimization)

Optimising content to be cited in answer engines and AI Overviews, not only to rank. The discipline is laid out in our AEO vs SEO playbook.

GEO (Generative Engine Optimization)

Optimising for visibility inside generative AI answers across assistants and AI search surfaces. How it relates to AEO and SEO is in GEO vs AEO vs SEO.

SERP APIs & infrastructure

SERP API

An API that returns parsed search engine results page data as structured JSON, so you don’t scrape, render or maintain a crawler yourself. The full primer is what is a SERP API, and the build-vs-buy case is in web scraping vs SERP API.

Synchronous vs Asynchronous API

A synchronous API returns the result in the same request (seconds). An asynchronous API accepts a task and makes you poll for the result later (sometimes minutes) — cheaper for batch jobs but unusable when a user is waiting. We benchmarked the difference in SerpApi vs DataForSEO.

Proxy (Residential vs Datacenter)

An intermediary IP used to route requests. Residential proxies use consumer IPs (harder to detect, pricier); datacenter proxies use hosting IPs (cheaper, easier to block). The trade-off is in residential vs datacenter proxies.

Headless Browser

A real browser engine (Chromium, Firefox) run without a visible window, used to render JavaScript-heavy pages for scraping. Tooling choices are compared in Playwright vs Puppeteer.

CAPTCHA / Bot Detection

Challenges and behavioural signals search engines use to separate automated traffic from humans. Avoiding them at scale is the subject of how to scrape Google without getting blocked.

Rank Tracking

Measuring a site’s position for a set of keywords over time, usually by location and device. Build one from scratch in a rank tracker in 100 lines of Python.

Search Volume

How many times a keyword is searched in a period — a core input to prioritisation. You can estimate it without the Google Ads API.

Pricing & billing

Credit Expiry

Whether a provider’s prepaid credits or subscription quota expire if unused — never, on a fixed window, or each billing cycle. It can change the real cost of uneven workloads more than the per-1,000 rate; we checked eight providers, and modelled cost by volume in our SERP API cost calculator.

FAQ

What is a SERP API?

A SERP API returns parsed search results page data as structured JSON — organic results, AI Overviews, People Also Ask, local packs and other SERP features — so you don’t scrape, render or maintain a crawler. Send a query, get clean data back.

What’s the difference between SEO, AEO and GEO?

SEO optimises to rank in classic results; AEO optimises to be cited in answer engines and AI Overviews; GEO optimises for visibility inside generative AI answers across assistants. They overlap but target different surfaces.

What’s the difference between an AI Overview and AI Mode?

The AI Overview is the answer block above Google’s organic results that cites a few sources; AI Mode is Google’s conversational search experience. They are separate engines with largely different citation sets.

What is pixel position?

How far down the page, in pixels, a result actually appears — versus its ordinal rank. Ads and SERP features mean two same-rank results can sit at very different depths, so pixel position is often a truer visibility measure.

What does grounding mean in AI search?

Giving a language model external, retrieved facts (such as live search results) at query time, so its answer reflects current sources rather than only training data. It underpins retrieval-augmented generation and accurate AI search.

What is query fan-out?

When an AI search system breaks one question into several related sub-queries, runs them, and synthesises one answer — which is why AI citations increasingly come from pages that don’t rank for the original query.