> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://docs.vapi.ai/llms.txt.
> For full documentation content, see https://docs.vapi.ai/llms-full.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://docs.vapi.ai/_mcp/server.

# Core Models

At it's core, Vapi is an orchestration layer over three modules: the **transcriber**, the **model**, and the **voice**.

<img src="https://files.buildwithfern.com/https://vapi.docs.buildwithfern.com/1cea4d1eb082394533cb1df548d411b982b730c4f915f2fcc4de2df07c16797a/static/images/quickstart/quickstart-banner.png" />

These three modules can be swapped out with **any provider** of your choosing; OpenAI, Groq, Deepgram, ElevenLabs, PlayHT, etc. You can even plug in your server to act as the LLM.

Vapi takes these three modules, optimizes the latency, manages the scaling & streaming, and orchestrates the conversation flow to make it sound human.

When a person speaks, the client device (whether it is a laptop, phone,
etc) will record raw audio (1’s & 0’s at the core of it).

This raw audio will have to either be transcribed on the client device
itself, or get shipped off to a server somewhere to turn into
transcription text.

That transcript text will then get fed into a prompt & run through an LLM
([LLM inference](/glossary#inference)). The LLM is the core intelligence
that simulates a person behind-the-scenes.

The LLM outputs text that now must be spoken. That text is turned back
into raw audio (again, 1’s & 0’s), that is playable back at the user’s
device.

This process can also either happen on the user’s device itself, or on a
server somewhere (then the raw speech audio be shipped back to the user).

The idea is to perform each phase in realtime (sensitive down to 50-100ms level), streaming between every layer. Ideally the whole flow [voice-to-voice](/glossary#voice-to-voice) clocks in at \<500-700ms.

Vapi pulls all these pieces together, ensuring a smooth & responsive conversation (in addition to providing you with a simple set of tools to manage these inner-workings).