Depends on the technology you use.
Usually its called name value pair. Query string refers to the whole string after ? sign. Then depending on technology used that query string is parsed and normally appears as the dictionary.
For example, http://www.example.com?foo=bar&foo1=bar1:
Request["foo"] yields "bar"
Request["foo1"] yields "bar1" for asp
or $_GET["foo"] -> "bar" for php and so on.
It's called "query string" as you can see in wikipedia.
The query.
http://tools.ietf.org/html/rfc3986#section-3.4
Depends on the technology you use. Usually its called name value pair. Query string refers to the whole string after ? sign. Then depending on technology used that query string is parsed and normally appears as the dictionary. For example, http://www.example.com?foo=bar&foo1=bar1: Request["foo"] yields "bar" Request["foo1"] yields "bar1" for asp or $_GET["foo"] -> "bar" for php and so on.
Its the query, or sometimes the query string.
To pinch a useful diagram from the URI RFC:
The 'foo' only is called String Parameters of the URL Query