What is Propagation?

From Novara Support Knowledgebase

Once you have registered your new domain, an update process called Propagation is needed before your new domain will be recognised over the internet. The same can be said when changes are made to the DNS servers for an existing domain.

Propagation is where old results for DNS records need to expire from the caches of DNS servers across the internet. While some servers may return the new result immediately, others may return the old value until the cached result is aged out. This is a gradual process and can take some time to complete over the entire internet. Local DNS's will pick up the changes first and then the changes will "propagate" further afield until all DNS's on the internet now have the new values for your domain.

As mentioned above, this process can take some time to complete fully, but for most cases this time frame will not exceed 24 hours