By Daniel Smith

• The Internet is a global network connecting millions of computers. More than 190 countries are linked into exchanges of data, news and opinions.
• In September 2014, the total number of websites with a unique hostname online exceeded 1 billion. This is an increase from one website
(info.cern.ch) in 1991.
• Unlike online services, which are centrally controlled, by design, the
Internet is decentralized. Each Internet computer, called a host, is independent. Operators can choose which Internet services to use and which local services to make available to the global Internet community.
• No one actually owns the Internet, and no single person or organization controls the Internet in its entirety. The Internet is more of a concept than an actual tangible entity, and it relies on a physical infrastructure that connects.

An intranet is a private computer network or single Web site that an organization implements in order to share data with employees around the world.
What intranets do
Intranets start by publishing web pages about company events, health and safety events. As more features get added an intranet can become essential to the operation of an organisation.
It becomes a portal that provides access for what workers need.
The intranet is protected from the internet by firewalls so they will need to log on with a secure password. If you are working outside of the organisation to access the intranet you could use a VPN
(virtual private network) This means all communications between the intranet and the user’s personal computer are encrypted.

Extranet is kind of a network like Intranet but your business is connected with external people like your suppliers, vendors, partners, customers or other businesses. Extranet is private network so that you can securely share information.
What extranets do
An extranet can be viewed as part of a company intranet that is extended to users outside the company.
Companies can use extranet to exchange large volumes of data. Extranet should be more efficient because everyone has access to the same data in the same format. All extranet communications can be encrypted over a VPN, it should also be more secure than sending data over the public internet.

LAN (local area network) is a computer network that interconnects computers within a limited area such as a home, school, computer laboratory, or office building, using network media.
The server has applications and data storage that are shared in common by multiple computer users.
A local area network may serve as few as two or three users (for example, in a home network) or as many as thousands of users.
A LAN server may also be used as a Web server if safeguards are taken to secure internal applications and data from outside access.
In some situations, a wireless LAN may be preferable to a wired LAN because it is cheaper to install and maintain.

WAN (wide area network) is a network that exists over a large-scale geographical area. A WAN connects different smaller networks, including local area networks (LAN), this ensures that computers and users in one location can communicate with computers and users in other locations.
WAN can be done either with the help of the public transmission system or a private network.
WANs are similar to a banking system, where hundreds of branches in different cities are connected with each other in order to share their official data.
A WAN is similar to a LAN just on a larger scale, TCP/IP is the protocol used for a WAN in combination with devices such as routers, switches, firewalls and modems.

A CAN (campus area network) is a network of multiple interconnected local area networks (LAN) in a limited geographical area. A CAN is smaller than a wide area network (WAN)
CANs own shared network devices and data exchange media.
CAN can link up to 2032 devices

A PAN (personal area network ) is a computer network used for data transmission among devices such as computers, telephones and personal digital assistants. You can use these networks to transfer files including email and calendar appointments, digital photos and music.
Personal area networks can be constructed with cables or be wireless. USB and FireWire technologies often link together a wired PAN.
while wireless PANs typically use Bluetooth or sometimes infrared connections.
Personal area networks generally cover a range of less than 10 meters (about 30 feet). PANs can be viewed as a special type of local area network that supports one person instead of a group.