A QueryString is a part of a uniform resource locator (URL) that assigns values to specified parameters. It fits between the resource parts and the fragment part in the URL encoding:
Encodes the given data using URL-encoding, also known as percent encoding.
The characters 0-9, A-Z, and a-z are unchanged by the encoding, as are the characters '-', '_', '.', and '~'. All other characters are encoded in hexadecimal, using the percent sign. Thus a space character is encoded as "%20", and the Unicode snowman (☃) is encoded as "%E2%98%83".