The domain name is in fact a name that registrars provide to the general public for easier access to their websites.
Domain names are the names given to sites which provide an easier way to remember instead of the raw IP addresses, this is as amatter of fact the name you type in the web browser which is later submitted to the Domain Name server. The rules for creating a domain name are rather strict, as their main part being the label (this is the part between the dots) the characters used can only be letters, digits or hyphens with the longest length admissible of 63. Initially all the labels had to start with a letter, but this rule has been waived and now a label can start with a digit too. The domain names are case insensitive. Every domain ends with a top level domain, which can be chosen from a limited range of country codes or generic name. The most common used top level domains are: .com, .net, .org and from the country codes: .co.uk, .us, .it, .tk.
With the explosion of the internet, the domain names trade and registration reached the status of a full grown business. There are now deals reaching millions of dollars and with them an entirely new brand of abuses were advented. Originally the domain names were supposed to be relevant and with a high degree of hierarchy, but in the quest of finding and maintaning memorable names this rule is pretty much ignored. For example the .com domain was initially designed only for commercial sites, but you can easily find even non profit organisations with a .com website. The most malignant type of abuse though is the cybersquatting, which means the acquirement of a domain very similar to a legitimate, very trafficked site, this is also known as typosquatting.