A query string is the part of a uniform resource locator (URL) containing data that does not fit conveniently into a hierarchical path structure. The query string commonly includes fields added to a base URL by a Web browser or other client application, for example as part of an HTML form.
eg: [https://www.google.com/search?q=iphone&ie=utf-8&oe=utf-8&client=firefox-b] will be tidy up as:
(1) q = iphone
(2) ie = utf-8
(3) oe = utf-8
(4) client = firefox-b