What would be a DNS from your mind? DNS could be Domain Name Service or Domain Name System.
By right a domain name will referring to the DNS setting and understand which web server or server should it go and an Internet User could only able to get the page work from their Browser.
Basically, DNS could be the group in 2 major group where I will separate it to parent DNS and child DNS. With Parent DNS, it meant that the DNS of your domain name set that referring to your DNS server such as ns1.mickgenie.com and ns2.mickgenie.com.
Once the parent DNS setting up, the domain will connect to the DNS server and you will have A, CNAME, MX, TXT, and so on record to refer so the subdomain, email services and some rules called from TXT will done accordingly.
Below is some of the record available.
1. Address Record (A record),
A record normally used by an IPs only where it could resolve to 4 blocked of IP which something like 127.0.0.1 and you shall not point it to a domain base such as mickgenie.com and this will cause it not working.
2. Canonical Name (CNAME),
CNAME used a user-friendly domain name such as mickgenie.com to allow a user do not need to remember the IPs based address and this is easily for a web services to connect to different server if they have more than 1 server within the subdomain.
3. Mail Exchange(MX),
MX record used for the email services and it used to recognize if you have more than 1 email server and if you have backup email services.
4. Text (TXT),
TXT record is widely used when a DNS services contain a Sender Verify Framework(SPF) were used to protect spamming record, etc.
TXT also used when you have a domain key such as Yahoo! email services protection.