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

# Core Concepts

> Essential concepts for understanding Threadify's execution tracking system

Understanding these core concepts will help you effectively use Threadify to build and validate real-time execution graphs.

## Core Building Blocks

### [Threads](./threads)

A thread represents a complete business process execution—like a customer checkout, loan application, or insurance claim.

### [Steps](./steps)

Steps are the individual actions or operations within a thread, representing specific parts of your business process.

### [Contracts](./contracts)

Contracts define business rules and validation logic that enforce how steps should execute and relate to each other.

### [Sub-steps](./sub-steps)

Sub-steps allow you to break down complex steps into smaller, trackable operations within a parent step.

## Advanced Features

### [References](./references)

References link threads to external system identifiers like order IDs, customer IDs, or support tickets.

### [Hash Chain](./hash-chain)

The hash chain provides cryptographically verified ordering and integrity for all steps in a thread.

### [Access Levels](./access-levels)

Access levels control who can view, modify, or interact with threads and their data.

### [Notifications](./notifications)

Notifications are real-time WebSocket events that allow your application to react to execution graph changes.

### [Idempotency](./idempotency)

Idempotency ensures that recording the same step multiple times has the same effect as recording it once.

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Ready to start? [Begin with the Quick Start guide](../quickstart) to see these concepts in action.