To register a domain name, you must go to a domain registrar such as Go Daddy or Namecheap. You pay a registration fee to register the domain for an initial period (usually 1 year) and will then need to pay your registrar for renewals each time a renewal is due.
Nameservers are the servers that stores the DNS records for a domain. Each domain should have at least two nameservers for redundancy reasons. The nameservers are usually provided by the registrar (the company used to register the domain) but they can be changed to a different company so that the registrar and company hosting the DNS records are different.
When changes are made in a DNS settings panel, those settings then get applied to the nameservers for that domain.
You can check which nameservers are on a domain by doing a whois lookup.
DNS stands for Domain Name System. It’s the system used by domain names to publish information, particularly, details about where servers on the Internet are hosting the domain’s website and email service. The owner of a domain sets up the DNS settings on their nameservers. This is usually done with the company the domain was registered with. They add the settings for where their website is hosted. When someone visits the domain name, that visitor’s browser will check the DNS settings on the domain to see where on the Internet it should go to fetch the page from.
The same process happens when an email is sent. The server being used by the email sender will query the DNS records on the domain to see what server (email provider) the email should be delivered to.