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title: Key Concepts
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### 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/guides/workflow/node).

***

### 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/guides/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**

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**Differences in Available Node**

1. The [End node](/en/guides/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/guides/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/guides/workflow/node/start) include: `sys.query`, `sys.files`, `sys.conversation_id`, `sys.user_id`. Built-in [variables](/en/guides/workflow/variables) for Workflow's start node include: `sys.files`, `sys_id`.

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