Phrase Search is a type of search

Search engine technology

Modern web search engines are complex software systems using the technology that has evolved over the years. There are several categories of search engine software: Web search engines , database or structured data search engines , and mixed search engines or enterprise search...

 that allows users to search for documents containing an exact sentence or phrase opposed to being limited to keywords

Keywords

Keywords are the words that are used to reveal the internal structure of an author's reasoning. While they are used primarily for rhetoric, they are also used in a strictly grammatical sense for structural composition, reasoning, and comprehension...

More recently, phrase search is one of the more important terms associated with optimising the textual content of web pages in such a way that it is likely to be found by someone searching for a certain string of text and further information based upon that search.