This tutorial shows you how to setup your Raspberry PI 4 as a headless server. This is a server without a monitor, keyboard and mouse connected to it. With this approach all you need is a network connection to install, control and administer your Raspberry PI 4.
After following the instructions in this tutorial, you have a clean Raspbian based server installed that is accessible over your network with SSH. All you need is a Raspberry PI 4, a micro SD-card and a power supply.