Overview of different layers of domain system

1. User makes local to resolver. 2. Resolver has a list of nameservers. Each nameserver has one or more pieces of the whole domain tree's data. 3. Namserver has information of different zones. It periodically updates from master files or foreign nameservers.

Contents of your DNS cache

From windows command promt you can type ipconfig /displaydns to view your current DNS cache content. You can also clear dns cache by typing ipconfig /flushdns.
DNS Cache

Root nameserver - Top Level Domain

There are currently 13 root nameservers with the name letters.root-server.net where letters are A to M. They respond for the root namespace domain, and redirects requests for a particular top-level domain (TLD) to that TLD's nameservers.
Top Level Domain

Mail Exchanger Record

An MX record or Mail exchanger record is a DNS resource record specifying how Internet e-mail should be routed. MX records point to the servers that should receive e-mail, and their priority relative to each other.When an e-mail message is sent through the Internet, the sending mail transfer agent which in my case is my local mail server, makes a DNS query requesting the MX record for the recipient's domain names. Recipient's domain name is the portion of the e-mail address following the "@". This query returns a list of host names of mail exchange servers accepting incoming mail for that domain, together with a preference number. The sending agent then attempts to establish an SMTP connection to one of these servers, starting with the one with the smallest preference number.If no MX records were present, a second request is made for the A record of the domain instead. The MX mechanism provides the ability to run multiple mail servers for a single domain I am attaching two DNS queries: 1. MX record 2. A record.
Mail Exchanger Record

google.com

I made query for NS and A record for google.com.