Before we start trying to hack into networks, I will spend a few lessons to explain what it is, what is a network, how it works and many details that will help you to understand what are you doing, why and what is its reason.
A network is a number of devices connected together, they are connected so they can share data (files, resources, etc), your home network, for example, is a source of data.
All networks (Wi-Fi and Wired) achieve this sharing of data, using the same principle, which I call, the device server. Basically, you need a device that acts as a server and then all the devices communicate with it, the server has access to the resources and all the other devices on the network are connected to it so they can access it too.
In a network, only one device has access to the internet (the server) and all the other devices have no access, but they can access it by connecting to the router. Consider the following example: One user (computer) connected to the network wanted to open the https://learninglms.gq website. The computer asked the router for the website, the router asked the internet, got an answer and it sends it directly to the device that asked for that website. That’s how a network works.
All of this data (requests and responses) are transferred as packets. In Wi-Fi networks, these packets are sent through the air, which means, that they are being broadcasted from the server to the device. If you are within range with these packets, you can sniff them, capture them and read them.