Any number of filtering criteria used to narrow the result set, such as color=blue or group_id=sandals or price=100-200. Facets, item groups and collection IDs can be used as filters. If filter_value has the form <min>-<max>, it is interpreted as a range. Filters with the same key are ORed together and filters with different keys are ANDed together by default. Only results that match the filters are returned. Boolean values are serialized with the first letter capitalized (e.g., True / False) as a convention.