The Internet: (not) a Series of Tubes
The Internet is "a global system of interconnected networks" that communicate via Internet Protocol (TCP/IP). TCP/IP defines the way data is packaged and communicated between machines, allowing for ad hoc extension of the network and addressing for every object attached to the network. Individual machines are known by their IP Address, which is a unique number indicating that specific device.
The video above outlines the basic mechanisms for how the Internet works. The core concepts that are crucial to understand are:
"The Internet" is a system of computers connected by a wire. (In some cases the "wire" might be a cellular phone signal or wifi signal, but there is always some form of directed data transmission that allows two computers to communicate.)
"Servers" are computers dedicated to sending information in response to requests from clients. Servers need to be fast, so they usually have more direct and more persistent connections to the Internet backbone.
"Clients" are computers making requests for information from servers. Clients are usually personal computers, so they don't have the same speed or persistence in their connection to the Internet. Clients also have IP addresses (every device on the Internet has an IP address).
The Internet is a system of computers who all package and communicate data in the same way so messages can be understood across machines. Similar to how the US Postal Service works, the messages can be in any language and form, but the envelope must adhere to strict standards in order to be properly delivered.
"Messages" sent on the Internet get broken down into "packets," which each take the fastest path to reach their destination IP address. Each packet might take a different route in order to adjust dynamically for data speeds.
"Routers" direct the packet traffic on the Internet. Wherever multiple computers or networks connect, there is a router. Routers direct individual packets on the speediest path to their final destination, usually through a series of other routers (commonly referred to as "nodes" when discussing traffic paths).
Since sometimes seeing this visualized in different ways is helpful, here is another helpful video that explains how the Internet works: