# Internet Fundamentals/Introduction
## The Internet
### What is the Internet?

* The Internet is a global Wide Area Network (WAN).
** A Network is a group of interconnected devices.
** A Wide Area Network (WAN) is a network that covers a large area.
** A Local Area Network (LAN) is a network that covers a small area.

### What are the main advantages of the Internet?

* Communication : Electronic mail (Email) and social media.
* Education : search engines and webpages.
* Entertainment : online games and online media.
* Online services : online shopping and online banking.

### What are the main disadvantages of the Internet?

* Threat to personal information : possible loss of name, address, credit card number,...
* Spamming : unwanted Emails that serve no purpose.
* Cybercrime : malware, ransomware, stealing of identities,...
* Virus attacks : cause a system to crash and may delete important data.

### History of the Internet

* In the 1950s, the United States Defense Department formed the Advanced Research Projects Agency (ARPA) with the purpose of developing technology.
* ARPA’s scientists could not easily communicate or share information, so they created a network of computers, which they called ARPAnet.
* In the 1970s, the TCP/IP protocol was developed, this protocol allowed the separate networks to communicate with each other.
* The joining of these networks created a huge WAN which came to be known as the Internet.

## The World Wide Web (WWW)
### What is the World Wide Web (WWW)?

* The World Wide Web (WWW) is a collection of different websites that can be accessed through a web browser.
** A website is a group of webpages hosted on one web server.
** A web server is an Internet server that serves webpages to the web browser.
** A web browser is an application that displays webpages.

### What is the difference between the World Wide Web (WWW) and the Internet?

* The Internet is a global WAN, and the WWW is an Internet service.

### How the World Wide Web (WWW) works?

* When a user makes a request over the Internet, the web browser sends this request to a web server, and the web server accepts and responds to it by storing and transferring webpages to the web browser.

### How are web pages transferred from servers to clients?

* Any resource connected to the WWW is identified by its Uniform Resource Locator (URL).
** A Uniform Resource Locator (URL) is the address of a WWW page.
** Example : http://www.example.com/...
* When the URL of a web page is identified, a protocol called Hyper Text Transfer Protocol (HTTP) sends a command to the web server.
** Hyper Text Transfer Protocol (HTTP) is a protocol which enables communication between web clients and web servers.
* Once the web server has transmitted the requested page, the web page can be displayed with Hyper Text Markup Language (HTML).
** Hypertext Markup Language (HTML) is the standard language for creating and displaying web pages.

### History of the World Wide Web (WWW)

* In 1990, the WWW was invented by Tim Berners-Lee.
* He created three technologies (HTML, URL and HTTP), which allowed to use the Internet to link one document directly to another.

## Internet connectivity
### What is needed to connect to the Internet?

* Internet Service Provider (ISP) : a business that provides a connection to the Internet.
* Modem : a piece of hardware that allows a device to connect to the Internet over a telephone line.
* Router : a piece of hardware that allows several devices to connect to a single Internet connection.

### Common methods of Internet connection

* Dial-up : an Internet connection which uses a telephone line and requires a landline.
* Digital Subscriber Line (DSL) : an Internet connection which uses a telephone line, but doesn’t require a landline.
* Cable TV : a wired Internet connection which uses Cable TV lines.
* Wi-Fi : a wireless Internet connection which uses radio waves.
* Satellite : a wireless Internet connection which uses satellites orbiting the Earth.
* 3G, 4G, and 5G : wireless Internet connections which uses cellular networks.

## Cloud computing
### What is cloud computing?

* Cloud computing is the process of storing and using services online, rather than storing them locally on a device.

### What are the main advantages of cloud computing?

* File storage : access files, documents and Emails from any device.
* File sharing : share files with several people at the same time.
* Backing up : protect your files.

### What are the main disadvantages of cloud computing?

* Copyright : possible loss of legal rights.
* Security : vulnerability to security attacks.
* Storage : expense of storage.