KDE Connect is a project to communicate across all your devices. For example, with KDE Connect you can receive your phone notifications on your desktop computer, control music playing on your phone from your desktop, or use your phone as a remote control for your desktop. To achieve this, KDE Connect:
implements a secure communication protocol over the network, and allows any developer to create plugins on top of it.
Has a component that you install on your desktop
Has a KDE Connect client app you run on your phone.