WHAT IS DNS?
Domain Name System or DNS is what translates domain names into IP addresses for computers to understand. It also supplies a list of mail servers which accept emails for each domain name.
Within the DNS, each domain selects a combination of name servers for its DNS records – this is where other name servers will look for information regarding the domain.
What are cached DNS records?
Name servers remember or cache DNS records to speed up DNS. Your Internet Service Provider’s name servers tend to remember the IP address once you’ve visited a website so that next time you visit the IP address can be found more quickly.
Your Internet Service Provider does this using the cached DNS record. It undertakes this process in cycles which explains why after you make changes to your DNS some visitors might not notice as they are viewing a cached version.