The IRS refunding people who have filed: How long do I have to wait for my refund? If I paid in do I get that back plus what I withheld? How do I know what I get back?

I am looking for answers with the IRS refunding people who have already filed. How do I know what I get back is correct? How do I know what I'll get back? How long do I have to wait? Do I get back what I paid in + what I withheld? I can't find anything on any website. Any help would be great.