XRIs are a new kind of identifier on the Internet, similar to URIs or e-mail addresses. However, a single XRI can be used for different services, such as a website, e-mail, skype, icq or any other. They are therefore neither website nor e-mail addresses alone; they can be both at the same time, and more.

An i-name is a reassignable XRI used for personal or organizational digital identity. I-names starting with '=' are intended for individuals. I-names starting with '@' are intended for organizations.

An i-number is a persistent XRI and can be seen as the 'invisible' half behind an i-name.

Put simply, an i-number uniquely identifies an XRI authority and contains the actual 'information' (services) of an XRI, while i-names are human readable names for those authorities. This is similar to the relation between IP addresses and domain names in the traditional Internet identifier infrastructure.