Data refers to any sort of information that is stored in a computer or on the internet. A user can organize, store and manipulate information as they wish. Before data is put into the internet the infrastructure must be in place for someone to access the internet and they must make a number of decisions. They must decide how they will send or upload the data, who will be able to access the data, who can change the data and if others will be able to share it. The answers to these questions will dictate the process the person uses to incorporate the data into the internet.
Packet switching is a way to transfer a file. When sending a file from one terminal to another the file is broken down in packets. These packets include additional info: where they're coming from, where they're going, what original order they should be in and where they are in relation to the original file. The packets will most likely arrive at their destination out of order. They are then reassembled in the correct order. Packet switching is more efficient than trying to transfer a file as one complete chunk. It may help to think of the file as a house you want to move from California to Florida. If you try to move the house all in one piece then it becomes slower and much harder. If the house is broken into first the kitchen, then the living room and so on the trucks may take different routes with the different pieces, but they all get to the same destination. Then they can be put back together correctly. (Analogy from Where the Wizards Stay Up Late by Katie Hafner) (See also TCP and IP)
A Peer to Peer network (P2P network) is a type of decentralized network in which individual nodes in the network (called "peers") act as both suppliers and consumers of resources. Any "peer" can download pieces of a file from any other "peer". This is in contrast to a centralized client server network where client nodes request access to resources provided by a central server. Advantages to P2P is that it is faster, "peers" can be close together or far apart and data will not be lost like in a centralized server if the server crashes. This is similar to a group of friends who need to know where Becky's house is for a party. The friends do not need to get Becky's address from Becky herself, but can get it from any of the other friends going to the party who know Becky's address. (See also Server)
An example of this is P2P file sharing. Once "peers" download a file completely they become "seeders". "Leechers" are the "peers" downloading a file. "Leechers" can download pieces of a file from multiple "seeders" at one time. Once the pieces of file (packets) arrive at the "leecher" they can be reassembled into the original file. The "leecher" then becomes a "seeder" and can share pieces of the file with other "peers".
The internet can be accessed wirelessly or a direct connection can be used using several different types of wires. Infrastructure is important because the stronger it is the greater access you have to the internet. Just like with the Parthenon in Greece without its strong infrastructure it could not have been built or used as a center for culture during the Common Era. (see also Internet Speed (Connection Types and Internet Service Provider)
Accessing the internet wirelessly uses Radio Frequency Signals (RF) in conjunction with an Internet Service Provider. A computer is connected to a router using a signal (so a person can be anywhere in their home and connect), which is connected to a modem, then the ISP takes over. The ISP will wire your house that is connected to a transmitter that transmits an RF signal to a tower that will connect a person to the internet. The signal may go through several towers before it reaches its destination.
The Internet backbone may be defined by the principal data routes between large, strategically interconnected computer networks and core routers on the Internet. These data routes are hosted by commercial, government, academic and other high-capacity network centers, the Internet exchange points and network access points, that interchange Internet traffic between the countries, continents and across the oceans. Internet service providers, often Tier 1 networks, participate in Internet backbone exchange traffic by privately negotiated interconnection agreements, primarily governed by the principle of settlement-free peering. (wikipedia)
When data is sent over the internet the data packets are sent over many public networks. On these public networks many people can access the information in those packets. To keep anyone, but the intended recipient, from accessing the information it must be encrypted by the sender and then decrypted by the recipient. Keys (secret values and mathematical formulas) are used to encrypt and decrypt data packets. Only a person with the matching key as the sender can decrypt the data packet to retrieve the information. There are many different cryptosystems, or ways to encrypt a data packet. This is similar to a treasure chest. Encrypting the data is like putting it into a chest and locking it with a key. No one else can open it unless they have the chest's key. That person is the intended recipient.
The Caeser Cipher is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. For example, with a left shift of 3, D would be replaced by A, E would become B, and so on. The method is named after Julius Caesar, who used it in his private correspondence. (Wikipedia)
Digital and analog are a way of describing quantity, such as fish. Digital is either yes or no, on or off. If someone asks you how many fish you have you can describe the number by holding up 8 fingers (or digits). You either have the fish or you don't. Analog is more like an analogy that can describe something that varies in quantity. If someone asks you how big your fish are you can show a size with your hands to show approximately how big the fish are. Computers use binary code (a series of 0's and 1's) to determine whether to apply power to something or not. This creates what a person sees on their computer screen. (Fish analogy is from the youtube video below. It is a video from a 1983 educational television series Bits and Bytes)