The Internet Committee for Assigned Names and Numbers, a committee commonly known as ICANN, is the controlling force behind the domain names that organize every website that exists on the internet. Domain names are organized in an efficient way based on three levels: top level domains, second level domains, and third level domains.
The main top level domains are com, net, org, and the country code domains. Below that it gets split up into varying names based on whatever the website owner requires.
Domains are incredibly important to many businesses and are vital in keeping up virtual appearances and brand recognition. The difficulty with multiple top level domains is that when one domain name is registered, it is also available in a similar form on another top level domain; this has caused many instances of fraud, copyright infringement, and frustration for large businesses who wish to control all similar domains to protect their company.