In order to search for some specific tag only, use tag: prefix, e.g. tag:quiz
In order to exclude or ignore games with some specific tag, use -tag: prefix, e.g. -tag:christmas
You can also search by multiple tags, for example: tag:quiz -tag:christmas
Keep in mind, when prefixes are used, all whitespaces must be replaced with _ (underscore), e.g. tag:skill_based
And of course, everything can be used at the same time. Query tag:christmas -tag:quiz new year will search for games with tag Christmas, excluding games with Quiz tag, and with words New Year in title or description.