Question

When using jQuery BBQ they are using the words “querystring” and “fragment”.

What is the difference btween the two?

Answer 1

In the definition of a URL (see e.g. here):

Fragment URLs

The URL specification en vigeur at the
writing of this document ([RFC1738])
offers a mechanism to refer to a
resource, but not to a location within
a resource. The Web community has
adopted a convention called “fragment
URLs” to refer to anchors within an
HTML document. A fragment URL ends
with “#” followed by an anchor
identifier. For instance, here is a
fragment URL pointing to an anchor
named section_2:

http://somesite.com/html/top.html#section_2

The #section_2 part is also called “the fragment”. Its interpretation is up to the user agent (AKA client AKA browser), though the universal convention is that it’s the anchor of an <a> tag to which the browser is asked to position itself.

The Query String, as explained here, is the part of the URL that’s passed to the server-side program — normally after a ? and up to but excluding the # if any. So, in:

http://server/path/program?query_string#thefrag

the query string would be query_string and the fragment would be thefrag.