To check any domain records and mapping there are many online tools available for example one of the tool is available as below which can be used to check the DNS records:
For detailed review with wiki you can look into the link here: Domain Name System – Wikipedia
DNS Propagation
Updating all the ISP providers with the mappings across the world called DNS propagation which can be trigger when DNS record changes. For example the propagation shown below which can take 24 to 72 hours time to complete:
