> ## Documentation Index > Fetch the complete documentation index at: https://algolia.com/llms.txt > Use this file to discover all available pages before exploring further. # Algolia glossary > Terms used at Algolia and their definitions. ## API Client A program that provides an abstraction over the raw Algolia [API](/doc/glossary#application-programming-interface-api), hiding implementation details to make development for [Subscribers](#subscriber) easier in the language of their choice. [Learn more](/doc/libraries/sdk) ## API key A string with alphanumeric characters used to control access to Algolia's [API](/doc/glossary#application-programming-interface-api), determining what is allowed to do, such as searching an [Index](#index), or adding new [Records](#record). [Learn more](/doc/guides/security/api-keys) ## Affinity A [Facet-Value pair](#facet-value-pair) that reflects [End-User](#user)'s preferences. ## Algolia AI Certain Algolia Services with an ability to train or adapt via use, such as [NeuralSearch](/doc/guides/ai-relevance/neuralsearch/get-started), [Dynamic Re-Ranking](/doc/guides/algolia-ai/re-ranking), [AI Synonyms](/doc/guides/algolia-ai/dynamic-synonym-suggestions), [Query Categorization](/doc/guides/algolia-ai/query-categorization), [Advanced Personalization](/doc/guides/personalization/advanced-personalization/what-is-advanced-personalization) and [Recommend](/doc/guides/algolia-recommend/overview) features: Frequently Bought Together, Alternative Items, Looking Similar, Content Based Alternative Items, and otherwise identified by Algolia. ## Application A siloed set of [indices](#index). Data cannot be shared between applications. ## Application ID A string with alphanumeric characters as a unique identifier for Algolia [applications](#application). ## Application Programming Interface (API) A software intermediary that allows pieces of software to interact with each other. The Algolia API describes how the [Subscribers'](#subscriber) systems can interact with Algolia Services. [Learn more](/doc/rest-api) ## Click-through rate (CTR) The percentage of tracked searches with at least one click [Event](#event). A tracked search is a search with the [`clickAnalytics`](/doc/api-reference/api-parameters/clickAnalytics) parameter set to true. [Learn more](/doc/guides/search-analytics/concepts/metrics#click-through-rate) ## Conversion rate The percentage of tracked searches with at least one conversion [Event](#event). A tracked search is a search with the [`clickAnalytics`](/doc/api-reference/api-parameters/clickAnalytics) parameter set to true. [Learn more](/doc/guides/search-analytics/concepts/metrics#conversion-rate) ## Dashboard The [Subscriber's](#subscriber) administrator interface to Algolia Services. The Dashboard is hosted by Algolia. ## Event An action performed by a [User](#user) on [Subscriber's](#subscriber) app or website. [Learn more](/doc/guides/sending-events) ## Facet A specific characteristic for describing [index](#index) items, such as color or brand. [Learn more](/doc/guides/managing-results/refine-results/faceting) ## Facet-Value pair A pair made of a [Facet](#facet) name and a value. For example, if "priority" and "quality" are two Facets, "priority:high" and "quality:high" are two Facet-Value pairs. ## Filter A [Facet-Value pair](#facet-value-pair) used to select results with a specific facet value for a given [facet](#facet) name. [Learn more](/doc/guides/managing-results/refine-results/filtering) ## Generative Experiences Certain Algolia Services that leverage generative artificial intelligence, such as Ask AI, Agent Studio, and Generative Experience Guides. ## Index A container for a set of [Records](#record) that can be searched together. [Learn more](/doc/guides/sending-and-managing-data/send-and-update-your-data) ## Insights API Algolia's API designed to ingest [Events](#event) from [Subscriber's](#subscriber) apps and websites. [Learn more](/doc/rest-api/insights) ## InstantSearch A collection of open source software libraries that let [Subscribers](#subscriber) build Algolia search interfaces for their frontend application. The InstantSearch libraries are built on top of [API Clients](#api-client). [Learn more](/doc/guides/building-search-ui/what-is-instantsearch/js) ## Library A collection of reusable software, designed to help developers solve common problems. A library is often targeted to be used with a specific software platform or operating system. ## Primary Serving Region Region selected by [Subscriber](#subscriber) and used by Algolia as the primary region for Search query processing. ## Profile Designates a set of information about a single [End-User](#user), including their [Affinities](#affinity) based on enriched [Events](#event) and audience segment to which the [End-User](#user) belongs. ## Record [Subscriber](#subscriber) items stored in an Algolia [Index](#index) for retrieval. [Learn more](/doc/guides/sending-and-managing-data/prepare-your-data) ## Search Request A group of one or more [search queries](#search-query) sent in a single HTTP request. ## Search query A sequence of characters typed into a search box, or specific filters or facets applied to a search. ## Subscriber A customer of Algolia Services, such as Search or Recommend. ## User Customers or end-users of Algolia [Subscribers](#subscriber) who interact with Algolia Services, such as Search and Recommend. ## User token A unique string of alphanumeric characters that uniquely identifies a [User](#user) throughout [applications](#application). A user token must contain only alphanumeric, `=`, `-`, `/`, or `_` characters and be between 1 and 128 characters in length. [Learn more](/doc/guides/sending-events/concepts/usertoken)