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Internet & Internet services Cheat Sheet by

What is the Internet and what is it good for? Networks, packets, routing, WWW, email, search...

What is a Network?

When you have more than one computer or device connected together, you have a network.

A network allows devices to send each other data in the form of 0's and 1's (bits or binary digits).

Four Kinds of Networks

Local Area Network; wired with NIC & network cables; for small to medium­-sized areas like a room or a building
Wireless Local Area Network; wireless, uses Wi-Fi techno­logy, connected by WNIC (wireless NIC), routers, access points; for small areas like a building
Wide Area Network; wired, may use submarine cables; connects many networks together over a large area (i.e. city, country, the world)
Wireless Personal Area Network; wireless, uses Bluetooth techno­logy, connected by WNIC (wireless NIC); devices connect directly to each other; for a very small area (a room)

Network Devices

Network interface card; a card inside a device or computer that allows it to connect to a network; usually has a port, i.e. a place to connect a network cable; a WNIC is a wireless NIC and lets you connect to Wi-Fi or Bluetooth.
Network cable
A long cable that carries electrical signals from the NIC of one device to the NIC of another one.
Connects different types of networks together, i.e. a LAN to a WAN; they help to send packets of data to the correct destin­ation, i.e. receiver.
Allows devices to connect to others to share data; non-in­tel­ligent (they send data everywhere and don't try to look for the correct receiver).
Allows devices to connect to others to share data; intell­igent (they send data only to the correct receiver).
Connects LANs together to make one large LAN.
"Modulator/Demodulat­or"; carry digital signals over an analogue cable (like a telephone cable); usually used to connect to an ISP (Internet Service Provider)

The World Wide Web

The WWW or World Wide Web is one of the most popular platforms for internet services.
A website is a set of pages built using techno­logies like HTML, CSS, and Javascript. Websites can be about any topic and do many different things.
Websites are stored on web servers, which use a protocol called HTTP to display websites.
HTTPS ("secure HTTP") is a secure version of HTTP. This means it keeps all the website's data private when you connect.
Web browsers are software apps that help users connect to websites. They include include Chrome, Firefox, Safari, Opera, etc...
A web browser has a large space to display websites, and other parts like navigation (back/­next) buttons, a reload button, and an address bar where URLs are entered.


A URL, or Uniform Resource Locator, shows where to find a file on the Internet.
"­htt­ps:­//" is the protocol. This URL uses the HTTPS protocol, which is used to send data securely.
"­ima­ges.te­cha­dvi­­m" is the website address. It is made up of the domain host (www), the domain name (techa­dvi­sor), and the domain type (com). Sometimes, there is also a country code, like "­uk" for the United Kingdom.
"­/cm­sda­ta/­sli­des­how­/36­340­08/­" is the path. This is like a list of folders that contain the file.
"­fun­ny_­tec­h_m­eme­­g" is the file name. This one ends in ".jp­g", so we know this is a JPEG image file.

Web Search

Search engine
A website, or part of a website, that allows you to search for different things, like text, pictures, music, or video. Examples of search engines include Google, Bing, Yahoo, Baidu, Yandex...
Search keyword
Also called search term. A word related to the kind of thing you're looking for. An example of search keywords might be "­Bla­ckpink video".
Search results
Things that a search engine returns after you search with certain keywords. For instance, searching with the keywords "­Bla­ckpink video" might return a list of music videos by Blackpink.

What is the Internet?

A worldwide network of networks
A global, public network of computers
The world's largest WAN
Not the same as an intranet!

What is the Internet Used For?

Many things! Includ­ing...
Browsing web pages using the World Wide Web (WWW)
Sending and receiving emails
Using search engines to do research, e.g. for school projects
Sharing files and inform­ation
Video confer­encing (face to face discussion using webcam, e.g. MS Teams or Zoom)
Voice calls (like Skype or Zalo)
Streaming music and video (like YouTube or Spotify)
Online banking
E-commerce, i.e. online shopping
Blogging (writing articles or journal entries) or vlogging (making video journals)
Social media
Playing multi-­player online games

Packets & Routing

To send data across the Internet, a router breaks it into small pieces called packets. These packets always carry a message or part of a message, and the IP address of the computer that sent the message (sender) and the computer that should get the message (receiver).

An IP address is like the address of a house. It tells the router where to find the receiver, so it can send the message to the right place. There are two kinds of IP addresses: IPv4 and IPv6.

Example of IPv4: 192.16­8.0.1
Example of IPv6: 2001:0­db8­:00­00:­000­0:0­000­:8a­2e:­037­0:7334

The router will look at its neighbours to find the best "­roa­d" to send the message. The "­roa­d" that the message takes is called its route. Routers look at the receiver's IP address to help them decide on the best route. This is called routing. Every packet can take a different route. If a network connection breaks down (e.g. because a cable breaks), routers can help packets find a new route. This is called re-routing. Eventu­ally, the packet will find its way to the right place. Yay!

How Email Works

Email is electronic mail. It's just like regular mail ("snail mail") but it's faster, because it uses the Internet.

Imagine Jack wants to send a paper letter from Ha Noi to his friend Joe in Ho Chi Minh City. Jack writes his letter, puts it in an envelope, and brings it to the post office in Ha Noi. On the envelope, he writes the address of his friend Joe, who should receive it (i.e. the receiver). He also writes his own address so it's clear who sent it (i.e. the sender). Next, the post office in Ha Noi takes his letter and sends it to the post office in Ho Chi Minh City. Then, the post office in Ho Chi Minh City sends a mail carrier to deliver the letter to his friend Joe.

Email is the same, but instead of a post office, email servers are used. Imagine Jack ( wants to send an email message to Joe ( Jack logs into his webmail, writes his message, adds a subject (e.g. "Hi Joe"), and includes Joe's email address ( in the "To:" field. When Jack clicks the Send button, the message moves into his outbox, and from there it is sent to Jack's email server (i.e. Jack's email server looks at the receiver's email address ( and sends the message over the Internet. The message is routed to Joe's email server (i.e., which receives the message for Joe. When Joe logs into his webmail, he finds Jack's message in his inbox.

Basic Email Vocabulary

A system for sending electronic mail.
Something that uses electric transi­stors or circuits, e.g. a computer.
email account
When you pay an ISP to use their email service, we say that you have an email account.
email address
A string of characters in the form 'usern­ame­@se­rve­' that identifies an email account. Email servers use this to know where an email message should go.
email server
A computer whose job is to send and receive email messages.
A website that allows you to send and receive email. ISPs that provide email accounts often provide webmail.
A piece of inform­ation that is sent somewhere (from a sender to a receiver).
A folder that contains messages received from other email users.
A folder that contains messages to be sent to other email users.

Parts of an Email Message

The main part of a message, containing most of the inform­ation.
The topic of a message; what a message is about. Stored in the "­Sub­jec­t:" field of an email message.
The person who sends the message. Stored in the "­Fro­m:" field of an email message.
The person who receives the message. Stored in the "­To:­" field of an email message.
carbon copied receivers
Other people who will receive copies of a message. Stored in the "­Cc:­" field of an email message.
The name of a message's sender. ex: Mr. Jack Johnson. Emails are note signed with a pen like letters are, so a sender will just type their name at the bottom of a message.
signature block
Extra inform­ation about the sender that appears in an email message below the signature. ex: Student, XYZ School, New Delhi, India.


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