[Prompt Templates](https://js.langchain.com/docs/concepts/prompt_templates/): LLM should read this page when needing to understand prompt templates in LangChain, implementing different types of prompts, or working with message placeholders. (This page explains LangChain's prompt templates that help translate user inputs into instructions for language models. It covers three main types: String PromptTemplates for formatting single strings, ChatPromptTemplates for formatting lists of messages, and MessagesPlaceholder for inserting lists of messages at specific positions in prompts.)

