Thats a very good question. I personally am not Catholic but from what I understand, confession to a priest is very important if you have committed "mortal sins". Just so you know, most Protestant churches believe that all sins are equal and that confession is important, but not with a priest. Also, as far as the Holy Spirit goes, when Jesus died will all receive the holy spirit when we repent and give our lives to God through Christ, making us all equal in God's eyes, therefore the priests aren't the only ones that can forgive.
Here is a site with detailed info on what Catholics believe:
http://www.newadvent.org/cathen/11618c.htmIts pretty long so when you have a good chunk of time you can read it. Hope this helps.
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