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  * [ Get started ](/docs/get_started)

    * [ Introduction ](/docs/get_started/introduction)
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    * [ Get started ](/docs/expression_language/get_started)
    * [ Why use LCEL ](/docs/expression_language/why)
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  * Introduction 

On this page

#  Introduction

**LangChain** is a framework for developing applications powered by language
models. It enables applications that:

  * **Are context-aware** : connect a language model to sources of context (prompt instructions, few shot examples, content to ground its response in, etc.) 
  * **Reason** : rely on a language model to reason (about how to answer based on provided context, what actions to take, etc.) 

This framework consists of several parts.

  * **LangChain Libraries** : The Python and JavaScript libraries. Contains interfaces and integrations for a myriad of components, a basic run time for combining these components into chains and agents, and off-the-shelf implementations of chains and agents. 
  * **[ LangChain Templates ](/docs/templates) ** : A collection of easily deployable reference architectures for a wide variety of tasks. 
  * **[ LangServe ](/docs/langserve) ** : A library for deploying LangChain chains as a REST API. 
  * **[ LangSmith ](/docs/langsmith) ** : A developer platform that lets you debug, test, evaluate, and monitor chains built on any LLM framework and seamlessly integrates with LangChain. 

![Diagram outlining the hierarchical organization of the LangChain framework,
displaying the interconnected parts across multiple
layers.](/svg/langchain_stack.svg) ![Diagram outlining the hierarchical
organization of the LangChain framework, displaying the interconnected parts
across multiple layers.](/svg/langchain_stack_dark.svg)

Together, these products simplify the entire application lifecycle:

  * **Develop** : Write your applications in LangChain/L