Phrase searching narrows your search results by allowing you to define precisely how you want the words to appear. For example, if you are searching for information on job satisfaction then you are probably looking for those two words to appear right next to each other, with no other words in between, in the text of the document. To make sure that the database searches this correctly you can put quotation marks around your search term and force the database to search this as a phrase.
Be careful when you use phrase searching; if you put too many words in quotations the database will most likely not find any results. You want to only use phrase searching on established phrases - words that you can reasonably expect other authors used.