Participant observation, however, is sometimes called a form of subjective sociology, not because the researcher aims to impose their beliefs on the respondent (this would simply produce invalid data), but because the aim is to understand the social world from the subject's point-of-view.

This method involves "getting to know" the people being studied by entering their world and participating - either openly or secretly - in that world.  You put yourself "in the shoes" of the people you're studying to experience events in the way they experience them.