~HELP!!!~ Computer/ IT folks???

I have a 2nd interview with Bellsouth today in their web hosting department for a Helpdesk Analyst position. The manager who interviewed me told me that the job would involve a lot of email server and DNS server troubleshooting. He told me that he wants me to study the following: - DNS - C NAME - A NAME - MX RECORD - TELNET ...... does anyone here in this community have any quick info to offer that might give me a crash course on the above?