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

# Key Concepts

### Nodes

**Nodes are the key components of a workflow**. By connecting node with different functionalities, you can execute a series of operations within the workflow.

For core workflow node, please refer to [Block Description](/en/3.1.x/use/workflow/README).

***

### Variables

**Variables are used to link the input and output of node within a workflow**, enabling complex processing logic throughout the process. Fore more details, please take refer to [Variables](/en/3.1.x/use/workflow/variables).

***

### Chatflow and Workflow

**Application Scenarios**

* **Chatflow**: Designed for conversational scenarios, including customer service, semantic search, and other conversational applications that require multi-step logic in response construction.
* **Workflow**: Geared towards automation and batch processing scenarios, suitable for high-quality translation, data analysis, content generation, email automation, and more.

**Usage Entry Points**

<div class="image-side-by-side">
  <img src="https://assets-docs.dify.ai/2024/12/befca8ff01ac5dccf4d32bcab08b8a11.png" className="mx-auto" alt="" />

  <img src="https://assets-docs.dify.ai/2024/12/56521297208916676acaf1c59e968e41.png" className="mx-auto" alt="" />
</div>

**Differences in Available Node**

1. The [End node](/en/3.1.x/use/workflow/node/end) is an ending node for Workflow and can only be selected at the end of the process.
2. The [Answer node](/en/3.1.x/use/workflow/node/answer) is specific to Chatflow, used for streaming text output, and can output at intermediate steps in the process.
3. Chatflow has built-in chat memory (Memory) for storing and passing multi-turn conversation history, which can be enabled in node like LLM and question classifiers. Workflow does not have Memory-related configurations and cannot enable them.
4. Built-in variables for Chatflow's [start node](/en/3.1.x/use/workflow/node/start) include: `sys.query`, `sys.files`, `sys.conversation_id`, `sys.user_id`. Built-in [variables](/en/3.1.x/use/workflow/variables) for Workflow's start node include: `sys.files`, `sys_id`.

<CardGroup cols="2">
  <Card title="Edit this page" icon="pen-to-square" href="https://github.com/langgenius/dify-docs-mintlify/edit/main/en/guides/workflow/key-concepts.mdx">
    Help improve our documentation by contributing directly
  </Card>

  <Card title="Report an issue" icon="github" href="https://github.com/langgenius/dify-docs-mintlify/issues/new?title=Documentation%20Issue%3A%20once&body=%23%23%20Issue%20Description%0A%3C%21--%20Please%20briefly%20describe%20the%20issue%20you%20found%20--%3E%0A%0A%23%23%20Page%20Link%0Ahttps%3A%2F%2Fgithub.com%2Flanggenius%2Fdify-docs-mintlify%2Fblob%2Fmain%2Fen/guides/workflow%2Fkey-concepts.mdx%0A%0A%23%23%20Suggested%20Changes%0A%3C%21--%20If%20you%20have%20specific%20suggestions%20for%20changes%2C%20please%20describe%20them%20here%20--%3E%0A%0A%3C%21--%20Thank%20you%20for%20helping%20improve%20our%20documentation%21%20--%3E">
    Found an error or have suggestions? Let us know
  </Card>
</CardGroup>