Unread feeds

[tearinghair]

Can't believe I've only just noticed a large number of 'unread feeds' on the left of my Windows Live Mail. I started to delete them without opening, but then wondered whether they might be important; also I have inadvertently taken the heading off the list so I won't be able to see if they're there in future.
Please could someone enlighten me - what are these, do they matter, and could they have appeared without my noticing them? And is there anyway of deleting them in bulk?
Many thanks.

[tearinghair]

OK, I give up.

[McMouse]

I'm still thinking.