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# Chains

Using an LLM in isolation is fine for simple applications,
but more complex applications require chaining LLMs - either with each other or with other components.

LangChain provides the **Chain** interface for such "chained" applications. We define a Chain very generically as a sequence of calls to components, which can include other chains. The base interface is simple:

import BaseClass from "@snippets/modules/chains/base_class.mdx"

<BaseClass/>

This idea of composing components together in a chain is simple but powerful. It drastically simplifies and makes more modular the implementation of complex applications, which in turn makes it much easier to debug, maintain, and improve your applications.

For more specifics check out:
- [How-to](/docs/modules/chains/how_to/) for walkthroughs of different chain features
- [Foundational](/docs/modules/chains/foundational/) to get acquainted with core building block chains
- [Document](/docs/modules/chains/document/) to learn how to incorporate documents into chains

## Why do we need chains?

Chains allow us to combine multiple components together to create a single, coherent application. For example, we can create a chain that takes user input, formats it with a PromptTemplate, and then passes the formatted response to an LLM. We can build more complex chains by combining multiple chains together, or by combining chains with other components.

## Get started

import GetStarted from "@snippets/modules/chains/get_started.mdx"

<GetStarted/>
