A lot of research into google are treated as a few individual words and the search engine finds the relationships between words to find the best results on the web, in some cases Google search results would show a snippet chosen by the site and in other cases a relevant preview of the page text .
But when you put some of the questions in quotesGoogle makes sure to find those exact words in that exact order and usually the search results page would also display the quote in the correct context of the page.
Today, Google announced that the search results page will now always display the quoted words in the context of how they appear. For example, a previous exception was when words appeared in the page navigation menus or elsewhere that was not a useful snippet.
In the blog post, the company provides an example of a “Google Search” query in quotes. In the second search result, the phrase “Google Search” appears on the page because it is used in the alternate text of an image on the page, and while it does not appear as default text on the page, “Google Search” is included in bold in the snippet, along with a nearby phrase to give you an idea where to look.
Source: Lega Nerd