If you are looking for a specific phrase, just typing it into a search engine will probably not get you the results you were hoping for. Search engines might bring back pages that have all the words you entered, but those words most likely will not be in the order you intended or even anywhere near each other. For instance, say you had a very specific search query in mind such as:
Nobel Prize Winners 1987
Your results could bring back pages that have Nobel Prize, winners of prizes, 1987 winners of prizes, 1,987 winners of prizes..and the list goes on. Probably not what you were hoping for, to say the least.
However, using quotation marks around your phrases takes care of this problem. When you use quotation marks around a phrase, you are telling the search engine to only bring back pages that include these search terms exactly how you typed them in-order, proximity, etc. For example:
"Nobel Prize Winners 1987"
Your search results now will only bring back pages that have all these words in the exact order that you typed them in. This little trick saves a lot of time and frustration.