> ## Documentation Index
> Fetch the complete documentation index at: https://docs.getbutter.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Glossary

> Common terms in Voice AI and Telephony

## AI Terms

### LLM (Large Language Model)

The "brain" of the agent (e.g., GPT-4, Claude). It takes text input (transcript) and generates text output (response).

### RAG (Retrieval Augmented Generation)

A technique to give the LLM extra knowledge. We search your uploaded documents for relevant info and insert it into the prompt before the LLM generates an answer.

### STT (Speech-to-Text)

Also known as ASR (Automatic Speech Recognition). The process of converting the user's audio into text.

### TTS (Text-to-Speech)

The process of converting the LLM's text response into audio.

### Latency

The time delay between when the user stops speaking and the agent starts speaking. In conversational AI, lower is always better.

### Token

The basic unit of text for an LLM. Roughly 4 characters or 0.75 words. Pricing is often per 1,000 (1k) or 1 Million (1M) tokens.

***

## Telephony Terms

### SIP (Session Initiation Protocol)

The standard protocol used for VoIP (Voice over IP) calls. It sets up and tears down the connection.

### SIP Trunking

A method of delivering telephone services to a business over the internet using SIP. Allows you to use your own carrier with Butter AI.

### WebRTC

A technology that enables real-time voice/video communication in browsers and mobile apps. Butter AI uses this for low-latency communication between our servers and the AI models.

### DID (Direct Inward Dialing)

Industry term for a standard phone number.

### E.164

The international telephone numbering format (e.g., `+14155550100`). All numbers in Butter AI must use this format.

### IVR (Interactive Voice Response)

Traditional phone menus ("Press 1 for Sales"). Butter AI agents replace IVRs with natural language understanding.