Even if you own a domain name, nobody will able to reach the domain unless it is listed on a nameserver.
A nameserver is one of the most important types of a web server. If you have a web host, it is likely that they will have their nameservers in place with already DNS software installed. But if you do not have a host yet, then your domain registrar will have basic/default nameservers that you can use for free.
Every domain name will need to have at least two nameservers where the domain can be pointed at. If you wish for more protection on your domain, e.g. against spam, then you can use external nameserver companies like Cloudflare which will automatically filter out spam traffic. It can save you bandwidth.