They are totally independent of the query.
Filters determine the population to which a given query can apply.
Most of the major search engines support filters to greater or lesser degrees. Some also offer filter capabilities unique to themselves. For certain specialty searches or needs, you can use these unique filter capabilities to great advantage. You may want to check out the comparison chart in Topic 38 to see how the major engines stack up and which unique capabilities they offer. You may click on any of the topics above to go directly to it.