SIMPLE FILTERS..
Query filters contain criteria for which you can declare attribute values (or properties) that you wish to include or those you wish to omit, i.e. records get omitted or included for further processing. Thus filters represent ESSENTIAL CRITERIA. On the other hand, CRITERIA THAT ARE DESIRABLE can be assigned weights [some criteria are more important than others] and EACH DESIRABLE INSTANCE represented by values/properties, a score - i.e. by choosing criteria for ranking, you can discriminate among those who satisfy filter criteria or even among those for whom no filter criteria are specified. You can choose multiple occurrences of a filter or attribute and specify different sets of values (or ranges)/properties.

To summarise, FILTERS have an INCLUDE or OMIT action flag associated with them. There are two rules: 1) For non-hierarchical sets, you should NOT mix include and omit flags for the same criterion in different instances (i.e. when there are multiple occurrences of a criterion, you should either have only include or only omit flags associated with the individual instances of the criterion) 2) For hierarchical sets (e.g. Regions - World, Continents, Countries, States and Towns), you can use exclude flag only if you have specified include for its parent region (e.g. you may say "India-include and Assam-exclude in a set of two repeats or "World-include, Asia-exclude and India-include" in a set of three repeats of the region criterion. 

ATTRIBUTES for ranking have a WEIGHT and individual instances (values/properties) have a SCORE associated with them. It is not necessary to use the same criterion as BOTH filter and query at the same time (though this is permitted) - these are independent usages and you must decide what works best for you in each case (exception is when a criterion is categorised as compulsory, then you must use it).