Natural language processing (NLP) is the subdomain of artificial intelligence that explores different methods of using computers to understand, analyze, and process the huge amount of human language or text. Technically, NLP focuses on knowledge acquisition and manipulation of the natural language in order to develop tools and techniques to help the computer understand and accomplish the desired task. The process of NLP is done in two phases: data preprocessing and development of an algorithm. This chapter summarizes these techniques. The tools used for NLP are also included in the discussion. NLP is used in text classification, extraction, summarization, and many other areas, which are also discussed in the chapter.