Retrieval-Augmented Generation (RAG) merges retrieval methods with deep learning advancements to address the static limitations of large language models (LLMs) by enabling the dynamic integration of up-to-date external information. This methodology, focusing primarily on the text domain, provides a cost-effective solution to the generation of plausible but incorrect responses by LLMs, thereby enhancing the accuracy and reliability of their outputs through the use of real-world data. As RAG grows in complexity and incorporates multiple concepts that can influence its performance, this paper organizes the RAG paradigm into four categories: pre-retrieval, retrieval, post-retrieval, and generation, offering a detailed perspective from the retrieval viewpoint. It outlines RAG's evolution and discusses the field's progression through the analysis of significant studies. Additionally, the paper introduces evaluation methods for RAG, addressing the challenges faced and proposing future research directions. By offering an organized framework and categorization, the study aims to consolidate existing research on RAG, clarify its technological underpinnings, and highlight its potential to broaden the adaptability and applications of LLMs.

Retrieval-Augmented Generation (RAG)是一种合并检索方法和深度学习技术的方法，旨在通过动态整合最新的外部信息解决大型语言模型（LLMs）的静态限制，并通过使用真实世界的数据提供一种成本效益的解决方案来改进LLMs输出的准确性和可靠性。该研究将RAG范式分为四个类别，并从检索的角度提供了详细的视角，同时介绍了RAG的演进和领域的进展。此外，该论文还提出了针对RAG的评估方法，并提出了面临的挑战和未来的研究方向，旨在巩固现有的RAG研究，明确其技术基础，并突出其扩展LLMs的适应性和应用潜力。

大型语言模型的检索增强文本生成综述