Several comma-separated tags will be considered as logical AND between them. You can also use semicolon for logical OR. AND has a priority over OR and you cannot use parentheses for logical grouping. Asterisk (*) within a tag will be regarded as a mask for "any string".

Found in forums

> New DLC, Arma 2 : OA PMC
    FORUMS / Operation Arrowhead / General Discussion   ||  Tags: Dlc, Expansion, Pmc