By who, how and where are ballots counted?

I filled mine out at home by filling in bubbles with a pen then mailed it off to a PO box address. Who opens the envelope, what is their training and party affiliation and so on? How does the process work and who knows what the results of the submitted ballots are so far since it's almost 100% certain the final results will be the same - they used to announce winners after counting 1% of votes counted and so now more than 1% has been mailed already (33% per the news) so who has access to these numbers??? (this is in CA but I"m sure similar in other states).