Quick answer: Data framework for LLM apps — strong at RAG over your private data.
LlamaIndex is an open-source data framework designed to help developers build production-grade applications with large language models (LLMs). Created by LlamaIndex, it specializes in connecting LLMs to your private data through retrieval-augmented generation (RAG), a technique that retrieves relevant information from your data before feeding it to the LLM for more accurate and contextual responses.
The framework handles the complex plumbing of data ingestion, indexing, retrieval, and LLM integration. It works with various data sources—documents, APIs, databases—and multiple LLM providers, making it ideal for teams building knowledge-based applications that need to leverage proprietary or sensitive information without exposing data to external APIs.