How to read an Internet URL (Universal Resource Locator)
Here is the URL for the State Library of New South Wales

http://www.slnsw.gov.au/

http:// - the name of the protocol - now so standard that you don't need to put it in usually

www - world wide web - now also almost universal, except there is now www2

slnsw - the name of the server on which the Internet site resides. In this case, it is the State Library of NSW. Other big commercial servers like Geocities have thousands of different Internet sites on them.

gov - the kind of site it is. com., gov., edu., net (organisations) are the American designations, used in Australia. go., co., ed., etc are the British, also used in New Zealand.

au - the country in which the server is located. Only USA does not designate a country.
NB: the country code does not necessarily mean that the writer of the Internet site is from there. Many Australian sites are lodged on big commercial servers in the USA.

Everything after the country code exists to show the pathway in the Internet site - where the particular page you are looking at, or searching for, sits in relation to the rest of that Internet site.