Certificates

[krcmd]

I am very confused by certificates:

what are they for?
where are they located? duplicate locations?
is my computer safer or less safe with them on board?
should one or more of them be removed from the computer?
why does IE repeatedly warn me that MSN.com is trying to connect with blank?
what role do certificates have in timestamping?
why do I suddenly have so many?
public vs private?

where can I find a primer?

thank you all!