Parent of Working Directory

[Padraig O'Briain]

I have been reading the hg man page.

The entry for cat refers to the parent of the working directory. The 
entry for diff refers to the
working directory's first parent.

Are these the same?
Are they the first changeset output by hg parents?

The entry for status does not state what happens if no revision is 
specified. Does it show status with the parent of the working directory 
being the base revision?

Padraig