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  * [ Get started ](/docs/get_started)

    * [ Introduction ](/docs/get_started/introduction)
    * [ Installation ](/docs/get_started/installation)
    * [ Quickstart ](/docs/get_started/quickstart)
    * [ Security ](/docs/security)
  * [ LangChain Expression Language ](/docs/expression_language/)

    * [ Get started ](/docs/expression_language/get_started)
    * [ Why use LCEL ](/docs/expression_language/why)
    * [ Interface ](/docs/expression_language/interface)
    * [ Streaming ](/docs/expression_language/streaming)
    * [ How to ](/docs/expression_language/how_to/)

    * [ Cookbook ](/docs/expression_language/cookbook/)

    * [ LangChain Expression Language (LCEL) ](/docs/expression_language/)
  * [ Modules ](/docs/modules/)

    * [ Model I/O ](/docs/modules/model_io/)

      * [ Model I/O ](/docs/modules/model_io/)
      * [ Quickstart ](/docs/modules/model_io/quick_start)
      * [ Concepts ](/docs/modules/model_io/concepts)
      * [ Prompts ](/docs/modules/model_io/prompts/)

      * [ Chat Models ](/docs/modules/model_io/chat/)

      * [ LLMs ](/docs/modules/model_io/llms/)

      * [ Output Parsers ](/docs/modules/model_io/output_parsers/)

    * [ Retrieval ](/docs/modules/data_connection/)

    * [ Agents ](/docs/modules/agents/)

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    * [ More ](/docs/modules/memory/)

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  * Model I/O 

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#  Model I/O

The core element of any language model application is...the model. LangChain
gives you the building blocks to interface with any language model.

![Flowchart illustrating the Model I/O process with steps Format, Predict, and
Parse, showing the transformation from input variables to structured
output.](/assets/images/model_io-e6fc0045b7eae0377a4ddeb90dc8cdb8.jpg)

##  [ Conceptual Guide ](/docs/modules/model_io/concepts) ​

A conceptual explanation of messages, prompts, LLMs vs ChatModels, and output
parsers. You should read this before getting started.

##  [ Quickstart ](/docs/modules/model_io/quick_start) ​

Covers the basics of getting started working with different types of models.
You should walk through [ this section ](/docs/modules/model_io/quick_start)
if you want to get an overview of the functionality.

##  [ Prompts ](/docs/modules/model_io/prompts/) ​

[ This section ](/docs/modules/model_io/prompts/) deep dives into the
different types of prompt templates and how to use them.

##  [ LLMs ](/docs/modules/model_io/llms/) ​

[ This section ](/docs/modules/model_io/llms/) covers functionality related to
the LLM class. This is a type of model that takes a text string as input and
returns a text str