# Layer 9 · Applications & Interfaces

URL: https://justuju.org/layer/applications-interfaces/

Where people meet AI: chat assistants, copilots inside existing tools, and specialised apps.

Gives the layer above: Value to people, plus usage and feedback that flow back down the stack.
Needs from the layer below: Agents or orchestrated model calls from the layers below.

## Concepts

- [Chat assistants](https://justuju.org/concept/chat-assistants/): General-purpose chat apps where you type, talk or upload files, and an assistant answers, writes, searches and uses tools.
- [Voice & multimodal interfaces](https://justuju.org/concept/voice-multimodal/): Talking to AI out loud and showing it images or video, through phones, cars, speakers and glasses.
- [AI features inside products](https://justuju.org/concept/embedded-ai/): AI built into ordinary apps as buttons and features, where the app's own server calls a model API behind the scenes.
- [Copilots](https://justuju.org/concept/copilots/): AI built into the tools people already work in, such as code editors, documents and email, suggesting and increasingly acting while the person stays in charge.

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Justuju · https://justuju.org/ · Content CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Quote with a link to the page.