In the hosting industry, the Domain Name System (DNS) is one of the most critical pieces, right behind websites themselves. Without DNS, that website you've worked so hard on would be completely invisible. (Although it's possible to access some sites using only the IP address of their web server, this is not the case for virtual websites, which require that their hostname be included in the HTTP request header. Without a working DNS record, virtual websites are completely inaccessible.) But I've found that DNS is something that is not well understood by many website operators. The basics of creating A records (which translate a hostname to an IP address) are simple enough, but when it comes to understanding how changes are propagated in DNS, this is often something of a mystery.