Question about Indexes...

If I create a table and assign the column type for what will be the primary
key the value of "Serial", do I need to explicitly create an index in
addition?

I was thinking that a Serial, would automatically be a Unique Index wouldn't
it? I also set that field to the primary key... does that ensure an index is
created?

Just a little confused...

Also, while I am on the topic, does it do any good to create indexes on a
timestamp field?

Thanks in advance,
Alan