I’m going to be fairly high level on these because to be honest, if you are going to use them it’s because you need them. And the corollary, if you don’t know that you specifically need them, don’t use them. You can find them in the security tab of the instance properties screen. They can also be found in sys.configurations and changed using sp_configure.
I’ll be honest, I’ve never actually used either of these myself. They used with the Common Criteria for Information Technology Security Evaluation. The BOL entry for C2 Auditing says that it is going to be removed in a future version of SQL and that you should use the Common Criteria Compliance setting instead. Be warned, if you do need to use C2 Auditing make sure that you have plenty of space. It chews it up like crazy and if you run out of space for your audit files SQL will stop.
Common Criteria Compliance doesn’t appear to do any auditing but does change settings on your machine to bring you into compliance with Common Criteria (although there is an additional script you need to run) so again, don’t use this unless you have been specifically told you need it. Microsoft has a PDF with additional information here: Microsoft SQL Server Common Criteria.
I realize I’m not really giving you a lot of information here, but I’ll be honest, these settings are something you need to be aware of in case you need them, not something you should be really playing with unless you actually expect you’ll be working with them in the future.