ELI5: Explain Like I'm 5

Information retrieval

Information retrieval is like searching for something in a huge library. Imagine a library with millions of books in it. Instead of knowing the title or author of the book you are looking for, you only know some keywords that describe the book. Information retrieval helps you to search this library of books. It helps you find the books that contain your keywords so you can find the book you are looking for.