A domain name server (DNS), or simply, nameserver is a computer that stores domain name records . On the simplest level, a domain name server acts like a telephone directory – you can lookup a name and it will provide you with a number. In the case of a nameserver, you can lookup a domain name, eg. example.com and it will return the linked IP address.
An IP address is the machine-readable name for a computer connected to the Internet. Every computer connected to a network, including the one you’re using right now, has an IP address.