Nameservers are devices used for running Domain Name Service (DNS) servers. Their role is to make the connection between the name of a domain that you enter in the browser and the IP of the equipment that provides services to that domain (email, web hosting, FTP, and others). Without setting the correct domain nameservers, it will not be able to point to the device where its files, emails, etc. are hosted.
We offer free DNS service for all domains purchased from us whether or not you have hosting from us.