> For the complete documentation index, see [llms.txt](https://kerno.gitbook.io/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://kerno.gitbook.io/docs/core-concepts.md).

# CORE CONCEPTS

- [How Kerno Works](https://kerno.gitbook.io/docs/core-concepts/how-kerno-works.md): Understand how Kerno works, from indexing your codebase to validating code changes.
- [Codebase Indexing](https://kerno.gitbook.io/docs/core-concepts/codebase-indexing.md): Understand how Kerno builds a deterministic index of your codebase, keeps it up to date, and why it matters for accurate validation.
- [Test Environment](https://kerno.gitbook.io/docs/core-concepts/environment-setup.md): Understand how Kerno connects to your running application and its dependencies to test against your real stack.
- [Baseline Tests](https://kerno.gitbook.io/docs/core-concepts/scenarios-and-baselines.md): Understand how Kerno generates test scenarios for your endpoints, what a baseline is, and how both stay in sync as your code evolves.
- [Code Change Review](https://kerno.gitbook.io/docs/core-concepts/change-validation.md): Understand how Kerno reviews your code changes and catches breaking changes and unintended side effects before they ship.
- [Custom Rules](https://kerno.gitbook.io/docs/core-concepts/custom-rules.md): Understand how to customize Kerno with custom rules, how to create them, and how they apply to the tests it generates.
- [Memory and Learning](https://kerno.gitbook.io/docs/core-concepts/memory-and-learning.md): Understand how Kerno remembers what it learns about your codebase and improves over time.