The way the query works, if you have nothing checked in a box, then all values for that field are legal, for example if you checked nothing in any of the boxes, you would get the entire bug list.
The default value of this form should correspond roughly to a "personal" bug list.
For example, if you wanted to see all bugs reported against the X platform and assigned to jwz, you could ask for all bugs assign to jwz, then edit the URL in the "Location" box, adding the clause "&rep_platform=X-Windows" to the URL.
Here is a list of some of the field names you could use for additional unsupported searches ...
version rep_platform op_sys reporter area bug_file_loc short_desc
Bugzilla uses several non-standard Netscape extentions, but this does not seem to case any problem with other browsers. The lynx browser does work, but lynx seems to cache results of a .cgi. You'll sometimes need to press CONTROL-R to reload the screen to see an update.