Cloudflare becomes your new name server. It usually grabs the DNS records from your old name server, but you need to double check that it got them all.
Your domain registrar tells the world which Name Server people need to use for your domain lookup.
Thank you for the response.
You mentioned that I need to double check that Cloudflare got my old name servers all.
Would you inform how to check it as well?
Also, do you mean that my hosting server, Digital Ocean, doesn’t need any name server?
Not your name servers, but your regular DNS records, such as IP addresses for your web server, MX records for email (if you have email for that domain), or any CNAME records.
You would compare your Cloudflare DNS page to the DNS records on your web host.