Information retrieval refers to the task of finding material from a large corpus, usually stored on computers, to satisfy an information need. In this chapter, we trace the history of the field of information retrieval—from Vannevar Bush’s Memex device to today’s digital technologies. We discuss four phases of the history of information retrieval, culminating in today’s era of LLMs. We additionally describe metrics to evaluate information retrieval methods and systems. We conclude with a discussion of bias in information retrieval systems and ways in which information retrieval systems may cause harm.