query about blob analysis

Hi,

So i am trying to understand the blob analysis command which is used in my code foe vehicle detection... here us the command used:

vision.BlobAnalysis('BoundingBoxOutputPort', true, ... 'AreaOutputPort', true, 'CentroidOutputPort', true, ... 'MinimumBlobArea', 400);

i am unable to understand what this true, or false refers to because interchanging these gives errors. Can anyone explain what theses refer to?