DNS propagation is the time it takes for DNS changes on a domain name such as a change of nameservers to take full effect on all servers across the internet.
This is not an instant process due to a number of factors and can take up to 48 hours for propagation to take place, however, this is very rare and propagation usually happens in under an hour.
During the propagation process your website may show on certain servers in certain regions before others and depends on where the source server is located and where you or a visitor is located around the globe.
