Concepts and terminology.
- [Concepts and terminology](https://python.langchain.com/en/latest/getting_started/concepts.html)
Tutorials created by community experts and presented on YouTube.
- [Tutorials](https://python.langchain.com/en/latest/getting_started/tutorials.html)
## Modules [\#](\#modules "Permalink to this headline")
These modules are the core abstractions which we view as the building blocks of any LLM-powered application.
For each module LangChain provides standard, extendable interfaces. LanghChain also provides external integrations and even end-to-end implementations for off-the-shelf use.
The docs for each module contain quickstart examples, how-to guides, reference docs, and conceptual guides.
The modules are (from least to most complex):
- [Models](https://python.langchain.com/en/latest/modules/models.html): Supported model types and integrations.
- [Prompts](https://python.langchain.com/en/latest/modules/prompts.html): Prompt management, optimization, and serialization.
- [Memory](https://python.langchain.com/en/latest/modules/memory.html): Memory refers to state that is persisted between calls of a chain/agent.
- [Indexes](https://python.langchain.com/en/latest/modules/indexes.html): Language models become much more powerful when combined with application-specific data - this module contains interfaces and integrations for loading, querying and updating external data.
- [Chains](https://python.langchain.com/en/latest/modules/chains.html): Chains are structured sequences of calls (to an LLM or to a different utility).
- [Agents](https://python.langchain.com/en/latest/modules/agents.html): An agent is a Chain in which an LLM, given a high-level directive and a set of tools, repeatedly decides an action, executes the action and observes the outcome until the high-level directive is complete.
rtdocs_stable/api.python.langchain.com/en/stable/modules/indexes/document_loaders/examples/tomarkdown.html