The first section in bold contains critical requirements and a site will not be listed if any of the requirements are not met. For example; if you are a motorcyclist then it is of little use to you to have sites that do not allow motorcyclists listed. Not selecting that option will list both sites that do and do not allow motorcyclists. Likewise if you do not require chemical toilets disposal facilities or facilities for disabled then do not select these options as sites without them will not be listed.
The next two sections are prefered on site and nearby facilities. The touring site listing will return the sites that most meet your requirements in a descending order, i.e., the site that mostly matches your requirements first.