Whois Domain Name Lookup
Whois is a look up used to find out who owns certain domains. You can do a whois lookup on basically any kind of domain extension including .com.au .com .co.uk and more. Depending on the whois tool that you are using you may be able to only look up .com.au, .net.au and other australian domain names.
Most domain name registration companies will have a whois domain name lookup feature on your website so you can see if the domain name is owned. If you are looking at a UK based website chances are you won't be able to do a whois lookup on a .com.au domain name.
The information provided in a whois lookup can include: Registrant email, Tech Email, Name Servers they are using, Name, Address. Registration Date and more.
The whois lookup tool is great and useful if you are looking up information on domain names.