DNS or Domain Name System is the heart of the internet and computer networks which resolves the domain names into IP addresses. Some systems stores the resolved IP and domain name in the cache and uses them without querying them again and again from and DNS server or resolver. Simply DNS flush will remove all records in this cache and make the DNS cache empty.
How DNS Works?
DNS is the Domain Name System. DNS servers and solvers provide the translation between the IP address and domain name. For example, the windowstect.com is a domain name and translated or resolved into the IP address 184.108.40.206 . The services like HTTP and HTTPS are served via the IP address 220.127.116.11 but the users do not need to remember this IP address they only need to type the domain name. When the domain name is provided the configured DNS servers resolves this domain name into an IP address and the communication occurs over the IP addresses.
What Is DNS Cache?
As explained in the previous step the IP address and domain names are resolved by DNS servers. But resolving the domain names into IP addresses, again and again, makes the communication slow especially for web usage. DNS Cache is used to store these resolutions for a limited time in order to prevent asking for the same domain name and IP address resolution multiple times.
What Does DNS Flush Do?
Even storing the DNS resolutions in a cache seems very good practice and the method may create problems. For example, if the IP address of the specific domain changes the change will not affect unless the DNS cache is updated. Or a single domain name can be served via multiple IP addresses which may change regularly. DSN flush will delete and remove all previously saved cache entries.
In order to learn how to flush a DNS cache take a look to the following tutorial which explains te DNS flush for Windows, Linux and MacOSX and related versions.