> For the complete documentation index, see [llms.txt](https://docs.umbraco.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.umbraco.com/umbraco-cms/13.latest/implementation/learn-how-umbraco-works.md). # Learn how Umbraco works Get to know the Umbraco codebase. Developing an application requires knowledge about the tool you are working with. This section will give you an introduction to the underlying structure of Umbraco CMS.


Routing	The process from front-end user requests to content delivery.	Routing	routing-image (1).png
Custom routing	Learn how to work with custom URLs and custom MVC routes.	Custom Routing	c-routing-image (1).png
Controllers	Everything you need to know about the different types of controllers.	Controllers	controllers-image (1).png
Data persistence	Learn how to create, read, update, and delete data in the Umbraco database.	Data Persistence (CRUD)	datap-image (1).png
Composing	Customize the behavior of an Umbraco application at 'start up'.	Composing	composing-image (1).png
Services and Helpers	Learn how to use the core Services and Helpers when extending Umbraco.	Services and Helpers	services-image (1).png

## Test your application This section also includes documentation on different ways to run tests on your code and implementations. {% content-ref url="/pages/cNCTZvcZwY2bY5gQe0k1" %} [Integration Testing](/umbraco-cms/13.latest/implementation/integration-testing.md) {% endcontent-ref %} {% content-ref url="/pages/9Cd3jNcvQd91r9GQyWxA" %} [Unit Testing](/umbraco-cms/13.latest/implementation/unit-testing.md) {% endcontent-ref %} --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation by asking a question. Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters: ``` GET https://docs.umbraco.com/umbraco-cms/13.latest/implementation/learn-how-umbraco-works.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.