This is especially important in the field of natural language processing (NLP), where machines are tasked with making sense of unstructured text data. In this book, we will explore various techniques used in NLP to extract information from text or unstructured data. These techniques can identify entity names, locations, quantities, and more. This book explains how to create applications for information extraction (IE) that can effectively utilize the wealth of information present in natural language sources. The text covers document retrieval, information extraction, and text categorization technologies, highlighting commonalities in general principles and practical considerations.