> For the complete documentation index, see [llms.txt](https://docs.january.ai/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.january.ai/client-sdks/android-sdk/concepts.md).

# Core concepts

How the SDK models clients, end users, and food data.

* [Client lifecycle](/client-sdks/android-sdk/concepts/client-lifecycle.md): one client per signed-in account, coroutines, and cancellation.
* [User identity and timezone](/client-sdks/android-sdk/concepts/user-context.md): the scoped client, the end-user ID, and how days are counted.
* [Food discovery and servings](/client-sdks/android-sdk/concepts/food-lifecycle.md): from search to a full food and a portion you can log.