Networking is a good place to start to understand computer networks. You can also learn the main parts of how data is sent in this section. First, you can look at the network protocols that let devices talk to each other.
But you can check the routing section, which shows how data is sent on its way. Also, switching is the main way devices share data with each other.
Also, you should learn how to keep your network safe from bad access. So, make sure you know common attack types and how to stop them. For this, I suggest you check the network security and attacks section well.