DNS Watcher is designed to monitor your DNS servers. A DNS server is the server that is responsible for mapping your domain name into a numeric IP address. If it goes down, you have serious problems!

Why do I need to monitor it ?

Many people rely on either their ISPs server or a third-party DNS provider. Since you don't personally control these servers, you had better keep an eye on them and make sure they don't become misconfigured. ISPs, Web Hosting companies, and DNS providers change their configurations from time-to-time. Sometimes they sell out and are acquired by another business. This can happen without your being aware. Technically, they always notify you first, but with all the email we get these days, even the best system administrator might miss an important notice.

Similarly, maybe due to an accounting glitch your bill didn't get paid on time (credit card expirations will do this to you all the time!) or maybe your domain new renewal has expired.

The point is, DNS records are vitally important to your web service, and you had better have some form of monitoring to make sure the records are online.

Other useful software:

Have a look at Interactive DNS Query, a standalone interactive program that makes querying DNS records easy.