The KVM host is the physical system that runs the KVM guests. The KVM guests can only run inside a KVM host.
Setting up the KVM host environment is not as hard as you think, but there are a many things to consider before beginning the installation. Spending time planning your KVM host before you install it will save you a lot of trouble later on. The KVM host is running on physical hardware. Find out how you want to use your network devices and disks.