> For the complete documentation index, see [llms.txt](https://docs.cortex.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.cortex.io/ingesting-data-into-cortex/entities-overview/entities/adding-entities.md).

# Adding entities

Entities are the foundational building blocks that represent the components of your software ecosystem—services, domains, teams, and more—giving your organization a shared way to describe what exists and how it connects. Defined in YAML and enriched with live data from your existing tools, entities come together to form a catalog that serves as a single source of truth.

Cortex provides a set of built-in entity types that cover the most common building blocks of a software organization. These defaults give you a strong foundation out of the box, so you can start cataloging your ecosystem without needing to design a schema from scratch.

Learn how to add built-in entity types and how to create your own custom entity types in the sections below:

* [Services](/ingesting-data-into-cortex/entities-overview/entities/adding-entities/add-services.md)
* [Domains](/ingesting-data-into-cortex/entities-overview/entities/adding-entities/domains.md)
* [Teams](/ingesting-data-into-cortex/entities-overview/entities/adding-entities/teams.md)
* [Custom entity types](/ingesting-data-into-cortex/entities-overview/entities/adding-entities/entity-types.md)
* [Define dependencies](/ingesting-data-into-cortex/entities-overview/entities/adding-entities/dependencies.md)

{% hint style="success" %}
Want to learn more? Check out the Cortex Academy course on [Catalogs, Entities, and Relationships](https://academy.cortex.io/courses/understanding-understanding-catalogs-entities-and-relationships).
{% endhint %}