These three terms are often used as near-synonyms, although they each have slightly different meanings within the context of the internet.
IP addresses
IP, or ‘Internet Protocol’, is a set of rules that governs how data is sent over the internet. It works alongside a separate set of rules called TCP (Transmission Control Protocol) – the whole system is referred to as ‘the TCP/IP model’.
An IP address is a set of numbers separated by dots, such as ‘172.16.254.3’. It is used in the TCP/IP model to identify individual computers or devices (such as printers) on the internet.
Domain names
Long numbers are, of course, less easy to remember or recognise than words, so on the internet, a domain name is used as a way of expressing an IP address (sometimes more than one) in an easy-to-understand way.
Domain names are in two parts, separated by a dot – for example, xyzcompanylimited.com. The part to the left of the dot, usually the name of a business or person, is the mid-level domain. The part to the right of the dot (such as ‘com’, ‘uk’, ‘biz’ or ‘org’) is known as the top level domain.
URLs
The URL (Uniform Resource Locator) is the full address that you type into an internet browser to find a web page.
Each page in a website has its own URL. The home page usually has the basic URL, with subsidiary pages identified by an extra element (or ‘label’).
The different labels of a URL are separated by slashes, colons and dots. For example:
http://www.xyzcompanylimited.com/contact.htm
In this case:
- http is the protocol which is used to send the data for the website over the internet
- www is short for World Wide Web
- xyzcompanylimited.com is the domain name, which identifies the website’s IP address
- contact is the subpage
- htm means ‘HyperText Markup Language’, which is the code the web page is written in
