I don't know what smart folders are and — anyway, how to get rid of this nuisance?

In high priority, you click on it it loads up hundreds of emails. Are these copies from elsewhere? What the point?
I don't know what smart folders are and — anyway, how to get rid of this nuisance?

In high priority, you click on it it loads up hundreds of emails. Are these copies from elsewhere? What the point?
I have a load of 'high-priority' emails that I would like to mark as 'normal priority'.  Do I have to click on each individual message to mark as 'normal priority'? This would be very time consuming.  Is there any way I can select all the emails as one block and change all of them to 'normal priority' in one go?

Thanks.

Jonathan