You have recently updated your domain name to use new DNS records, or have updated your nameservers entirely, then you can check the propagation status using the following website…
https://www.whatsmydns.net/
DNS propagation nowadays is mostly gibberish – most providers will tell you DNS propagation can take up to 72 hours. This is rarely the case, and propagation completes in less than an hour globally. The delay is usually caused by ISPs caching those DNS records.