Harrison/update memory docs (#8384)

Co-authored-by: Bagatur <baskaryan@gmail.com>

docs/docs_skeleton/docs/modules/memory/chat_messages/index.mdx

@@ -0,0 +1,17 @@
+---
+sidebar_position: 1
+---
+# Chat Messages
+
+:::info
+Head to [Integrations](/docs/integrations/memory/) for documentation on built-in memory integrations with 3rd-party databases and tools.
+:::
+
+One of the core utility classes underpinning most (if not all) memory modules is the `ChatMessageHistory` class.
+This is a super lightweight wrapper which exposes convenience methods for saving Human messages, AI messages, and then fetching them all.
+
+You may want to use this class directly if you are managing memory outside of a chain.
+
+import GetStarted from "@snippets/modules/memory/chat_messages/get_started.mdx"
+
+<GetStarted/>

docs/docs_skeleton/docs/modules/memory/index.mdx

@@ -1,34 +1,62 @@
 ---
 sidebar_position: 3
 ---
-
 # Memory
 
-🚧 _Docs under construction_ 🚧
+Most LLM applications have a conversational interface. An essential component of a conversation is being able to refer to information introduced earlier in the conversation.
+At bare minimum, a conversational system should be able to access some window of past messages directly.
+A more complex system will need to have a world model that it is constantly updating, which allows it to do things like maintain information about entities and their relationships.
 
-:::info
-Head to [Integrations](/docs/integrations/memory/) for documentation on built-in memory integrations with 3rd-party tools.
-:::
+We call this ability to store information about past interactions "memory".
+LangChain provides a lot of utilities for adding memory to a system.
+These utilities can be used by themselves or incorporated seamlessly into a chain.
 
-By default, Chains and Agents are stateless,
-meaning that they treat each incoming query independently (like the underlying LLMs and chat models themselves).
-In some applications, like chatbots, it is essential
-to remember previous interactions, both in the short and long-term.
-The **Memory** class does exactly that.
+A memory system needs to support two basic actions: reading and writing.
+Recall that every chain defines some core execution logic that expects certain inputs.
+Some of these inputs come directly from the user, but some of these inputs can come from memory.
+A chain will interact with its memory system twice in a given run.
+1. AFTER receiving the initial user inputs but BEFORE executing the core logic, a chain will READ from its memory system and augment the user inputs.
+2. AFTER executing the core logic but BEFORE returning the answer, a chain will WRITE the inputs and outputs of the current run to memory, so that they can be referred to in future runs.
 
-LangChain provides memory components in two forms.
-First, LangChain provides helper utilities for managing and manipulating previous chat messages.
-These are designed to be modular and useful regardless of how they are used.
-Secondly, LangChain provides easy ways to incorporate these utilities into chains.
+![memory-diagram](/img/memory_diagram.png)
+
+
+## Building memory into a system
+The two core design decisions in any memory system are:
+- How state is stored
+- How state is queried
+
+### Storing: List of chat messages
+Underlying any memory is a history of all chat interactions.
+Even if these are not all used directly, they need to be stored in some form.
+One of the key parts of the LangChain memory module is a series of integrations for storing these chat messages,
+from in-memory lists to persistent databases.
+
+- [Chat message storage](/docs/modules/memory/chat_messages/): How to work with Chat Messages, and the various integrations offered
+
+### Querying: Data structures and algorithms on top of chat messages
+Keeping a list of chat messages is fairly straight-forward.
+What is less straight-forward are the data structures and algorithms built on top of chat messages that serve a view of those messages that is most useful.
+
+A very simply memory system might just return the most recent messages each run. A slightly more complex memory system might return a succinct summary of the past K messages.
+An even more sophisticated system might extract entities from stored messages and only return information about entities referenced in the current run.
+
+Each application can have different requirements for how memory is queried. The memory module should make it easy to both get started with simple memory systems and write your own custom systems if needed.
+
+- [Memory types](/docs/modules/memory/types/): The various data structures and algorithms that make up the memory types LangChain supports
 
 ## Get started
 
-Memory involves keeping a concept of state around throughout a user's interactions with an language model. A user's interactions with a language model are captured in the concept of ChatMessages, so this boils down to ingesting, capturing, transforming and extracting knowledge from a sequence of chat messages. There are many different ways to do this, each of which exists as its own memory type.
-
-In general, for each type of memory there are two ways to understanding using memory. These are the standalone functions which extract information from a sequence of messages, and then there is the way you can use this type of memory in a chain.
-
-Memory can return multiple pieces of information (for example, the most recent N messages and a summary of all previous messages). The returned information can either be a string or a list of messages.
+Let's take a look at what Memory actually looks like in LangChain.
+Here we'll cover the basics of interacting with an arbitrary memory class.
 
 import GetStarted from "@snippets/modules/memory/get_started.mdx"
 
 <GetStarted/>
+
+## Next steps
+
+And that's it for getting started!
+Please see the other sections for walkthroughs of more advanced topics,
+like custom memory, multiple memories, and more.
+

docs/docs_skeleton/docs/modules/memory/types/buffer.mdx

@@ -4,6 +4,6 @@ This notebook shows how to use `ConversationBufferMemory`. This memory allows fo
 
 We can first extract it as a string.
 
-import Example from "@snippets/modules/memory/how_to/buffer.mdx"
+import Example from "@snippets/modules/memory/types/buffer.mdx"
 
 <Example/>

docs/docs_skeleton/docs/modules/memory/types/buffer_window.mdx

@@ -4,6 +4,6 @@
 
 Let's first explore the basic functionality of this type of memory.
 
-import Example from "@snippets/modules/memory/how_to/buffer_window.mdx"
+import Example from "@snippets/modules/memory/types/buffer_window.mdx"
 
 <Example/>

docs/docs_skeleton/docs/modules/memory/types/entity_summary_memory.mdx

@@ -4,6 +4,6 @@ Entity Memory remembers given facts about specific entities in a conversation. I
 
 Let's first walk through using this functionality.
 
-import Example from "@snippets/modules/memory/how_to/entity_summary_memory.mdx"
+import Example from "@snippets/modules/memory/types/entity_summary_memory.mdx"
 
 <Example/>

docs/docs_skeleton/docs/modules/memory/types/index.mdx

@@ -0,0 +1,8 @@
+---
+sidebar_position: 2
+---
+# Memory Types
+
+There are many different types of memory.
+Each have their own parameters, their own return types, and are useful in different scenarios.
+Please see their individual page for more detail on each one.

docs/docs_skeleton/docs/modules/memory/types/summary.mdx

@@ -4,6 +4,6 @@ Conversation summary memory summarizes the conversation as it happens and stores
 
 Let's first explore the basic functionality of this type of memory.
 
-import Example from "@snippets/modules/memory/how_to/summary.mdx"
+import Example from "@snippets/modules/memory/types/summary.mdx"
 
 <Example/>

docs/docs_skeleton/docs/modules/memory/types/vectorstore_retriever_memory.mdx

@@ -6,6 +6,6 @@ This differs from most of the other Memory classes in that it doesn't explicitly
 
 In this case, the "docs" are previous conversation snippets. This can be useful to refer to relevant pieces of information that the AI was told earlier in the conversation.
 
-import Example from "@snippets/modules/memory/how_to/vectorstore_retriever_memory.mdx"
+import Example from "@snippets/modules/memory/types/vectorstore_retriever_memory.mdx"
 
 <Example/>