# Concepts & Glossary

> Source: https://docs.recombee.com/concepts-and-glossary

> For the complete documentation index, see [llms.txt](/llms.txt).

# Concepts & Glossary

This page describes the basic terminology that is used across this documentation.

[Catalog: A list of entities (Users or Items) along with their properties.](/getting_started#getting-started-catalog)

[Items: The content, products, or other entities that Recombee recommends or returns in search results.](/getting_started#getting-started-catalog)

[Item Properties: Attributes that describe Items, such as title, category, price, availability, or publication date.](/getting_started#defining-item-properties)

[Users: Users who interact with Items and get recommendations.](/api/users)

[User Properties: Optional attributes that describe Users, such as language, country, or subscription type.](/api/user-properties#subsection-values-of-user-properties)

[Series: Ordered collections of Items, used mainly in the video domain to represent shows, seasons, and episodes.](/integration_tips#modeling-series)

[Interactions: Events that record how Users engage with Items, such as views, purchases, ratings, or bookmarks.](/getting_started#getting-started-interactions)

[recommId: A unique identifier of a recommendation request, used to attribute subsequent Interactions to the recommendation that caused them.](/getting_started#reporting-successful-recommendations)

[Scenario: A specific place on a website, in an application, or in an email where recommendations or search results are presented. Each Scenario can be configured to match the intended behavior for the use case.](/scenarios)

[Logic: The recommendation model ensemble used to compute recommendations or search results in a Scenario.](/logics)

[Business Rules: Rules that adapt recommendation results to business requirements.](/reql#business-rules)

[Filters: Rules that determine which Items can appear in the results.](/scenarios/settings-in-admin-ui#filters)

[Boosters: Rules that make the recommender prefer some Items over others.](/scenarios/settings-in-admin-ui#boosters)

[Constraint: A rule that controls how frequently Items sharing a condition can appear in recommendation results.](/scenarios/settings-in-admin-ui#constraints)

[ReQL: Recombee Query Language, used to create custom Filters, Boosters, and advanced Item Segmentations.](/reql)

[Item Segmentation: A way to group Items into Segments based on their properties. The Segments can then be used to recommend the top categories, genres, artists, or a personalized ordering of homepage sections to users and can also be used in analytics.](/segmentations)

[Insights: Analytics in the Recombee Admin UI for exploring recommendation and Interaction data.](/insights)

[SDKs: Lightweight client libraries for integrating the Recombee API in various server-side and client-side programming languages.](/api_clients)

[Widget SDKs: Customizable components for adding Recombee recommendations and search to JavaScript or React applications.](/widget-sdks)

[No-Code Widgets: Recommendation and search components created in a visual editor in the Recombee Admin UI and added to a website using an embed code.](/no-code-widgets)