It is a worldwide system which has the following characteristics:
Internet is a world-wide / global system of interconnected computer networks.
Internet uses the standard Internet Protocol (TCP/IP)
Every computer in internet is identified by a unique IP address.
IP Address is a unique set of numbers (such as 188.8.131.52) which identifies a computer’s location.
A special computer DNS (Domain Name Server) is used to give name to the IP Address so that user can locate a computer by a name.
For example, a DNS server will resolve a name http://www.tutorialspoint.com to a particular IP address to uniquely identify the computer on which this website is hosted.
Internet is accessible to every user all over the world.
Intranet is system in which multiple PCs are connected to each other.
PCs in intranet are not available to the world outside the intranet.
Usually each company or organization has their own Intranet network and members/employees of that company can access the computers in their intranet.
Each computer in Intranet is also identified by an IP Address which is unique among the computers in that Intranet.