# App

> Extra software that runs next to Home Assistant on Home Assistant OS, like an MQTT broker or a file editor.

Source: https://contributors.home-assistant.io/glossary/app/

- In code: `addons`, `config.yaml`
- Also: apps
- Formerly: add-on, addon (old name: don't use it in new text)

Apps used to be called add-ons. The code still uses the old name, in the Supervisor API, in `config.yaml` keys, and in repository names like home-assistant/addons. In text, say app.

Not to be confused with the [companion apps](https://contributors.home-assistant.io/glossary/companion-app/) for phones and computers.

## Related terms

- [Supervisor](https://contributors.home-assistant.io/glossary/supervisor/): The part of Home Assistant OS that runs Home Assistant Core and apps, each in its own container, and handles their updates and backups.
- [Home Assistant OS](https://contributors.home-assistant.io/glossary/home-assistant-os/): The operating system made to run Home Assistant, with the Supervisor, apps, and backups. The recommended way to install Home Assistant.
- [Companion app](https://contributors.home-assistant.io/glossary/companion-app/): The Home Assistant app for Android, iOS, and macOS. It shows the frontend, and adds sensors, notifications, and widgets from the device.