Search engine coverage is full of terms that get used casually but rarely defined. Here are the ones you’ll actually encounter, explained plainly, with links to deeper coverage where we have it.
Core Mechanics
| Term | Plain-English Definition |
|---|---|
| Crawler (or spider, bot) | Automated software that follows links across the web to discover pages. See our full crawling/indexing/ranking guide. |
| Index | The stored, searchable database of pages a search engine has crawled and decided to keep. |
| Ranking algorithm | The system that scores and orders indexed pages for a specific query, based on hundreds of relevance and quality signals. |
| SERP | Search Engine Results Page — the page of results you see after running a search. |
| Metasearch engine | An engine with no index of its own that aggregates results from other search engines. Covered in our types of search engines guide. |
| Vertical search engine | A search engine specialized for one content type — academic papers, images, code, or products, for example. |
Privacy-Related Terms
| Term | Plain-English Definition |
|---|---|
| Browser fingerprinting | Identifying a specific device by combining details like screen size, installed fonts, and browser settings, without using cookies. See our fingerprinting explainer. |
| IP anonymization | Stripping or truncating part of an IP address before it’s logged, so the stored record can’t be traced back to one specific device. |
| Behavioral advertising | Ads targeted using a profile built from your past activity, as opposed to just the content of your current search. |
| Contextual advertising | Ads targeted only to the content of your current search query or page, with no profile of past behavior involved. |
| Do Not Track (DNT) | An optional browser signal requesting that a site not track you. Its use has declined because compliance was never legally mandatory in most jurisdictions. |
| Zero-log policy | A stated commitment not to retain records of user queries or IP addresses at all, ideally backed by an independent audit rather than just a claim. |
Content and Ranking Terms
| Term | Plain-English Definition |
|---|---|
| Featured snippet | A highlighted answer block shown above standard results, usually pulled directly from a ranking page’s content. |
| AI Overview / AI-generated answer | A synthesized summary generated by an AI system in response to a query, shown instead of or alongside a traditional ranked list of links. |
| Long-tail query | A longer, more specific search phrase, typically lower in search volume individually but often easier to match precisely. |
| Structured data / schema markup | Extra code on a webpage that explicitly labels its content (like a recipe, an FAQ, or a review) so search engines can understand and display it more precisely. |
| Safe search | A filtering setting that excludes explicit content from results, often on by default and adjustable in search settings. |
Business and Infrastructure Terms
| Term | Plain-English Definition |
|---|---|
| Open-source search engine | A search engine whose underlying code is publicly available for anyone to inspect, modify, or self-host. See our open source vs. closed source comparison. |
| Self-hosted instance | A copy of an open-source search tool run on someone’s own server rather than the original provider’s infrastructure. |
| Licensed results | Search results an engine displays that actually come from a different underlying engine’s index, via a commercial licensing agreement. |
Frequently Asked Questions
What’s the difference between a crawler and an index?
A crawler discovers pages by following links; the index is the stored database where a search engine keeps the pages it decided to include after crawling and analyzing them.
What does SERP stand for?
Search Engine Results Page — the page you see listing results after running a search.
Is browser fingerprinting the same as using cookies?
No. Cookies are small files a site stores in your browser and can delete. Fingerprinting identifies your device from characteristics like screen resolution and installed fonts, without storing anything on your device, which makes it harder to block or clear.
What is a zero-log search engine?
One that states it does not retain records of your search queries or IP address. The strength of that claim depends on whether it’s been independently verified through an audit, not just stated in a privacy policy.
Why does the difference between contextual and behavioral advertising matter?
Contextual ads are based only on your current search term; behavioral ads rely on a profile built from your history. An engine can display ads (and even claim to be ad-funded) while still avoiding the kind of tracking that behavioral advertising requires.
