DNS stands for
Domain Name System,
which is a form of domain name resolution.
DNS maps static and easily human readable textual (rather than numerical) names to IP addresses. A domain name server resolves the text domain name to the appropriate IP address. For example, entering “ping www.freertos.org” in the command console of a desktop computer will show a ping request being sent to the IP address 22.214.171.124 (at the time of writing – the IP address may change) because a DNS server resolved the string “www.freertos.org” to the IP address 126.96.36.199.
Like the IP address of the node running FreeRTOS+TCP, the IP address of a domain name server can be configured either statically as a parameter to FreeRTOS_IPInit(), or dynamically from a DHCP server.